GitReadAndGitLockTests functional tests fail intermittently

This issue is to track functional test failures in GitReadAndGitLockTests. We might need to add more logging to identify the cause.

Example of failing test:

2018-08-15T19:55:44.8402070Z => GVFS.FunctionalTests.Tests.EnlistmentPerFixture.GitReadAndGitLockTests.GitAliasNamedAfterKnownCommandAcquiresLock()
2018-08-15T19:55:44.8402910Z Test GVFS.FunctionalTests.Tests.EnlistmentPerFixture.GitReadAndGitLockTests.GitAliasNamedAfterKnownCommandAcquiresLock()
2018-08-15T19:55:44.8403466Z Failed at 7:55:44 PM taking 00:00:14.7328678
2018-08-15T19:55:44.8403988Z   Expected substring 'Waiting for 'GVFS.FunctionalTests.LockHolder'' not found in ''
2018-08-15T19:55:44.8404433Z   Expected: True
2018-08-15T19:55:44.8404794Z   But was:  False

It looks like the lock holder program is acquiring the lock, but the GVFS test is not making progress during this time:

2018-08-15T19:56:43.7458281Z [8/15/2018 7:55:28 PM] ReleaseExternalLockRequested
2018-08-15T19:56:43.7459306Z [8/15/2018 7:55:28 PM] ReleaseLockHeldByExternalProcess {"CurrentLockHolder":"GVFS.FunctionalTests.LockHolder (9776)","IsElevated":false,"EnlistmentId":"be90aca0fa3646ca875d3c85def8a65a","Result":"Released","DurationMS":6446,"LockHeldExternallyMS":6446,"ParseGitIndexMS":0,"UpdatePlaceholdersMS":0,"BlobsDownloaded":0,"BlobDownloadTimeMS":0,"CommitsAndTreesDownloaded":0,"CommitsAndTreesDownloadTimeMS":0,"SizeQueries":0,"SizeQueryTimeMS":0}
2018-08-15T19:56:43.7460607Z [8/15/2018 7:55:28 PM] Information {"Message":"GitStatusCache.IsReadyForExternalAcquireLockRequests: isCacheReady: True, shouldAllowRequest: True"}
2018-08-15T19:56:43.7461274Z [8/15/2018 7:55:28 PM] TryAcquireLockExternal {"LockRequest":"git status (5792)","IsElevated":true,"Result":"Accepted"}
2018-08-15T19:56:43.7461730Z [8/15/2018 7:55:29 PM] ReleaseExternalLockRequested
2018-08-15T19:56:43.7462949Z [8/15/2018 7:55:29 PM] ReleaseLockHeldByExternalProcess {"CurrentLockHolder":"git status (5792)","IsElevated":true,"EnlistmentId":"be90aca0fa3646ca875d3c85def8a65a","Result":"Released","DurationMS":1264,"LockHeldExternallyMS":1264,"ParseGitIndexMS":0,"UpdatePlaceholdersMS":0,"BlobsDownloaded":0,"BlobDownloadTimeMS":0,"CommitsAndTreesDownloaded":0,"CommitsAndTreesDownloadTimeMS":0,"SizeQueries":0,"SizeQueryTimeMS":0}
2018-08-15T19:56:43.7464180Z [8/15/2018 7:55:31 PM] TryAcquireLockExternal {"LockRequest":"GVFS.FunctionalTests.LockHolder (6652)","IsElevated":false,"Result":"Accepted"}
2018-08-15T19:56:43.7464757Z [8/15/2018 7:55:41 PM] ReleaseExternalLockRequested

Examples of builds with this test error:
18227.5