fix for interface conversion at metrics helper

[shaheerkootteeri]

What this PR does / why we need it

PR fixes a interface conversion issue that was causing the plugin commands to fail with error interface conversion: interface {} is nil, not string when the user has just orgID as the active context.
Tanzu CLI version : 1.1.0-alpha.0

Which issue(s) this PR fixes

Fixes #

Describe testing done for PR

make test was successful. Also validated the changes in local with just OrgId as active context.

Release note

Additional information

Special notes for your reviewer

Upon running plugin commands core CLI was throwing error below

panic: interface conversion: interface {} is nil, not string

goroutine 1 [running]:
github.com/vmware-tanzu/tanzu-cli/pkg/telemetry.computeEndpointSHAForTAEContext(0x1400010d980)
	/go/src/cayman_tanzu-cli/tanzu-cli/src/pkg/telemetry/metrics_helper.go:64 +0x1f8
github.com/vmware-tanzu/tanzu-cli/pkg/telemetry.computeEndpointSHAForContext(0x14001607ae0?, {0x14001308816?, 0x14001607b28?})
	/go/src/cayman_tanzu-cli/tanzu-cli/src/pkg/telemetry/metrics_helper.go:41 +0xa0
github.com/vmware-tanzu/tanzu-cli/pkg/telemetry.getEndpointSHA(0x14000d84ab0)
	/go/src/cayman_tanzu-cli/tanzu-cli/src/pkg/telemetry/metrics_helper.go:27 +0x54
github.com/vmware-tanzu/tanzu-cli/pkg/telemetry.(*telemetryClient).updateMetricsForPlugin(0x1400068e9c0, 0x14000d86600, {0x14000d834d0, 0x1, 0x1}, {0x140005ce450?, 0x10602349b?})
	/go/src/cayman_tanzu-cli/tanzu-cli/src/pkg/telemetry/client.go:221 +0x268
github.com/vmware-tanzu/tanzu-cli/pkg/telemetry.(*telemetryClient).UpdateCmdPreRunMetrics(0x14001607c98?, 0x14000d86600, {0x14000d834d0, 0x1, 0x1})
	/go/src/cayman_tanzu-cli/tanzu-cli/src/pkg/telemetry/client.go:116 +0x258
github.com/vmware-tanzu/tanzu-cli/pkg/command.newRootCmd.func1(0x14001607d68?, {0x14000d834d0, 0x1, 0x1})
	/go/src/cayman_tanzu-cli/tanzu-cli/src/pkg/command/root.go:145 +0x60
github.com/spf13/cobra.(*Command).execute(0x14000d86600, {0x14000d834d0, 0x1, 0x1})
	/go/pkg/mod/github.com/spf13/[email protected]/command.go:915 +0x4fc
github.com/spf13/cobra.(*Command).ExecuteC(0x1400062cc00)
	/go/pkg/mod/github.com/spf13/[email protected]/command.go:1068 +0x35c
github.com/spf13/cobra.(*Command).Execute(...)
	/go/pkg/mod/github.com/spf13/[email protected]/command.go:992
github.com/vmware-tanzu/tanzu-cli/pkg/command.Execute()
	/go/src/cayman_tanzu-cli/tanzu-cli/src/pkg/command/root.go:369 +0x28
main.main()
	/go/src/cayman_tanzu-cli/tanzu-cli/src/cmd/tanzu/main.go:15 +0x1c

[marckhouzam]

Thanks @shaheerkootteeri !
Sorry we missed this.
LGTM

[prkalle]

LGTM. Thanks