Account for InvalidOperationException in XunitLogger

[jeffkl]

Description

Some functional tests have been failing with this error:

System.InvalidOperationException : There is no currently active test.

 at Test.Utility.XunitLogger.Log(ILogMessage message) in D:\a\_work\1\s\test\TestUtilities\Test.Utility\XunitLogger.cs:line 32
   at NuGet.Common.LoggerBase.Log(LogLevel level, String data) in D:\a\_work\1\s\src\NuGet.Core\NuGet.Common\Logging\LoggerBase.cs:line 29
   at NuGet.Common.LoggerBase.LogInformation(String data) in D:\a\_work\1\s\src\NuGet.Core\NuGet.Common\Logging\LoggerBase.cs:line 55
   at NuGet.Test.NuGetPackageManagerTests.TestNuGetVSTelemetryService.EmitTelemetryEvent(TelemetryEvent telemetryData) in D:\a\_work\1\s\test\NuGet.Core.Tests\NuGet.PackageManagement.Test\NuGetPackageManagerTests.cs:line 8024

I guess under certain circumstances, the xunit APIs think a test isn't running and so writing to the ITestOutputHelper causes an exception. This change catches the exception and writes to Console.Out instead.

https://dev.azure.com/dnceng-public/public/_build/results?buildId=759945&view=ms.vss-test-web.build-test-results-tab&runId=19293168&resultId=102473&paneView=debug

PR Checklist

• Meaningful title, helpful description
• Added tests
• Link to an issue or pull request to update docs if this PR changes settings, environment variables, new feature, etc.