(GH-249) Fix "operation completed successfully" on stderr

It seems that many applications out there can return this error and
still exit with a zero exit code, when this is logged within the
PowerShell service runner, it should redirect that back to the info
stream and not count it as a fail point. If PowerShell does exit with a
non-zero status, then we should count the whole install as a failure no
matter what messages were logged. In this way the exit code 0 and the
message "The operation completed successfully" are not considered a
failure.

References:
https://rcmtech.wordpress.com/2012/03/06/vbscript-and-reg_binary-registry-values/
http://en.community.dell.com/techcenter/powergui/f/4833/t/19570669

>I've found the problem. The main problem is in reg.exe utility.
>Depending on the version reg.exe utility works differently. v5.1.x.x
(that I have on my XPSP3) works correctly, but v5.2.x.x does not work
as it is expected to work.

>"reg import" command:
>- when v5.1: returns "Operation completed successfully" to standard
OUTPUT stream
>- when v5.2: returns "Operation completed successfully" to standard
ERROR stream

>Moreover, it is probably a problem with PowerShell also :(
>PowerShell treats these streams differently and process ERROR stream
messages as errors. Which is correct imho.

src/chocolatey/infrastructure.app/services/PowershellService.cs

@@ -31,6 +31,7 @@ public class PowershellService : IPowershellService
     {
         private readonly IFileSystem _fileSystem;
         private readonly string _customImports;
+        private const string OPERATION_COMPLETED_SUCCESSFULLY = "The operation completed successfully.";
 
         public PowershellService(IFileSystem fileSystem)
             : this(fileSystem, new CustomString(string.Empty))
@@ -269,10 +270,22 @@ public bool run_action(ChocolateyConfiguration configuration, PackageResult pack
                         (s, e) =>
                             {
                                 if (string.IsNullOrWhiteSpace(e.Data)) return;
-                                failure = true;
-                                this.Log().Error(() => " " + e.Data);
+                                if (e.Data.is_equal_to(OPERATION_COMPLETED_SUCCESSFULLY))
+                                {
+                                    this.Log().Info(() => " " + e.Data);
+                                }
+                                else
+                                {
+                                    failure = true;
+                                    this.Log().Error(() => " " + e.Data);
+                                }
                             });
 
+                    if (exitCode != 0)
+                    {
+                        failure = true;
+                    }
+
                     if (failure)
                     {
                         Environment.ExitCode = exitCode;