Server certificate validation fails in latest Publisher

[vslepakov]

Describe the bug
Latest publisher version always reports OPC-UA server cert as invalid.
Exactly the same configuration (certs and createOptions) works just fine with Publisher 2.5.3

To Reproduce
Steps to reproduce the behavior:

1. Use Publisher with latest tag
2. use these createOptions:
   "{"Hostname":"publisher","Cmd":["--pf=/appdata/pn.json","--di=10","--si=10","--tp=/appdata/pki/trusted","--rp=/appdata/pki/rejected","--ap=/appdata/pki/own","--ip=/appdata/pki/issuer","--lf=/appdata/publisher.log"],"HostConfig":{"Binds":["/home/<path>:/appdata"]}}"
3. Put server certificate under /appdata/pki/trusted/certs
4. see following error in the log:

Opc.Ua.ServiceResultException: Certificate is not trusted.
SubjectName: DC=opcua-srv.i2uvk10rqycefadk3kvhbmhdgc.ax.internal.cloudapp.net, O=Prosys OPC, CN=SimulationServer@opcua-srv
IssuerName: DC=opcua-srv.i2uvk10rqycefadk3kvhbmhdgc.ax.internal.cloudapp.net, O=Prosys OPC, CN=SimulationServer@opcua-srv
 ---> Opc.Ua.ServiceResultException: Certificate is not trusted.
SubjectName: DC=opcua-srv.i2uvk10rqycefadk3kvhbmhdgc.ax.internal.cloudapp.net, O=Prosys OPC, CN=SimulationServer@opcua-srv
IssuerName: DC=opcua-srv.i2uvk10rqycefadk3kvhbmhdgc.ax.internal.cloudapp.net, O=Prosys OPC, CN=SimulationServer@opcua-srv
   at Opc.Ua.CertificateValidator.InternalValidate(X509Certificate2Collection certificates)
   at Opc.Ua.CertificateValidator.Validate(X509Certificate2Collection chain)
   --- End of inner exception stack trace ---
   at Opc.Ua.CertificateValidator.Validate(X509Certificate2Collection chain)
   at Opc.Ua.Client.Session.Open(String sessionName, UInt32 sessionTimeout, IUserIdentity identity, IList`1 preferredLocales, Boolean checkDomain)
   at Opc.Ua.Client.Session.Create(ApplicationConfiguration configuration, ConfiguredEndpoint endpoint, Boolean updateBeforeConnect, Boolean checkDomain, String sessionName, UInt32 sessionTimeout, IUserIdentity identity, IList`1 preferredLocales)
   at Opc.Ua.Client.Session.Create(ApplicationConfiguration configuration, ConfiguredEndpoint endpoint, Boolean updateBeforeConnect, String sessionName, UInt32 sessionTimeout, IUserIdentity identity, IList`1 preferredLocales)
   at Microsoft.Azure.IIoT.OpcUa.Protocol.Services.DefaultSessionManager.GetOrCreateSessionAsync(ConnectionModel connection, Boolean createIfNotExists) in D:\a\1\s\components\opc-ua\src\Microsoft.Azure.IIoT.OpcUa.Protocol\src\Services\DefaultSessionManager.cs:line 70
   at Microsoft.Azure.IIoT.OpcUa.Protocol.Services.SubscriptionServices.SubscriptionWrapper.GetSubscriptionAsync(SubscriptionConfigurationModel configuration) in D:\a\1\s\components\opc-ua\src\Microsoft.Azure.IIoT.OpcUa.Protocol\src\Services\SubscriptionServices.cs:line 415
   at Microsoft.Azure.IIoT.OpcUa.Protocol.Services.SubscriptionServices.SubscriptionWrapper.ApplyAsync(IEnumerable`1 monitoredItems, SubscriptionConfigurationModel configuration) in D:\a\1\s\components\opc-ua\src\Microsoft.Azure.IIoT.OpcUa.Protocol\src\Services\SubscriptionServices.cs:line 162
   at Microsoft.Azure.IIoT.OpcUa.Protocol.Services.SubscriptionServices.SubscriptionWrapper.ApplyAsync(IEnumerable`1 monitoredItems, SubscriptionConfigurationModel configuration) in D:\a\1\s\components\opc-ua\src\Microsoft.Azure.IIoT.OpcUa.Protocol\src\Services\SubscriptionServices.cs:line 176
   at Microsoft.Azure.IIoT.OpcUa.Edge.Publisher.Engine.WriterGroupMessageTrigger.DataSetWriterSubscription.OpenAsync(CancellationToken ct) in D:\a\1\s\components\opc-ua\src\Microsoft.Azure.IIoT.OpcUa.Edge.Publisher\src\Engine\WriterGroupMessageSource.cs:line 127
   at Microsoft.Azure.IIoT.OpcUa.Edge.Publisher.Engine.WriterGroupMessageTrigger.RunAsync(CancellationToken ct) in D:\a\1\s\components\opc-ua\src\Microsoft.Azure.IIoT.OpcUa.Edge.Publisher\src\Engine\WriterGroupMessageSource.cs:line 63
   at Microsoft.Azure.IIoT.OpcUa.Edge.Publisher.Engine.DataFlowProcessingEngine.RunAsync(ProcessMode processMode, CancellationToken cancellationToken) in D:\a\1\s\components\opc-ua\src\Microsoft.Azure.IIoT.OpcUa.Edge.Publisher\src\Engine\DataFlowProcessingEngine.cs:line 105
   at Microsoft.Azure.IIoT.Agent.Framework.Agent.Worker.JobProcess.ProcessAsync() in D:\a\1\s\common\src\Microsoft.Azure.IIoT.Agent.Framework\src\Agent\Default\Worker.cs:line 320
[18:09:45 INF] Worker: StandalonePublisher_0, Job: LegacyPublisher_vislepak-edge_publisher processing completed ...  (Microsoft.Azure.IIoT.Agent.Framework.Agent.Worker)
[18:09:45 INF] Worker: StandalonePublisher_0, start processing new job: LegacyPublisher_vislepak-edge_publisher, mode: Active (Microsoft.Azure.IIoT.Agent.Framework.Agent.Worker)
[18:09:45 INF]
   DIAGNOSTICS INFORMATION
   =======================
   # Messages invoked by the message trigger: 0
   # Messages Sent to IoT Hub: 0
   # Number of connection retries since last error: 0
   # EncodingBlock input/output count: 0/0
   # BatchBlock output count: 0
   # SinkBlock input count: 0
   =======================
 (Microsoft.Azure.IIoT.OpcUa.Edge.Publisher.Engine.DataFlowProcessingEngine)
[18:09:51 INF] Trying to create session 95922ac072ce7db850c4c8da9679c273db54dfb6... (Microsoft.Azure.IIoT.OpcUa.Protocol.Services.DefaultSessionManager)
[18:09:51 INF] 95922ac072ce7db850c4c8da9679c273db54dfb6 took 00:00:00.0357363. (Microsoft.Azure.IIoT.OpcUa.Protocol.Services.DefaultSessionManager)

Expected behavior
Certificate is trusted, session can be created exactly as 2.5.3 which works without any changes to the setup .

[cristipogacean]

fixed in #423