Mac: Double hydration race condition leads to sporadic failures of MultithreadedReadWriteTests.CanReadVirtualFileInParallel

[wilbaker]

Example failure:

2018-09-28T16:48:12.0939760Z 1) Failed : GVFS.FunctionalTests.Tests.EnlistmentPerFixture.MultithreadedReadWriteTests.CanReadVirtualFileInParallel()
2018-09-28T16:48:12.0940220Z   At least one of the reads failed
2018-09-28T16:48:12.0940410Z   Expected: null
2018-09-28T16:48:12.0941870Z   But was:  <System.IO.IOException: The process cannot access the file '/GVFS.FT/test/c6474bc299d348b68d54/src/GVFS/GVFS.FunctionalTests/Tests/LongRunningEnlistment/GitMoveRenameTests.cs' because it is being used by another process.
2018-09-28T16:48:12.0942170Z    at Interop.ThrowExceptionForIoErrno(ErrorInfo errorInfo, String path, Boolean isDirectory, Func`2 errorRewriter)
2018-09-28T16:48:12.0942320Z    at Microsoft.Win32.SafeHandles.SafeFileHandle.Open(String path, OpenFlags flags, Int32 mode)
2018-09-28T16:48:12.0942520Z    at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options)
2018-09-28T16:48:12.0942680Z    at System.IO.StreamReader..ctor(String path, Encoding encoding, Boolean detectEncodingFromByteOrderMarks, Int32 bufferSize)
2018-09-28T16:48:12.0942810Z    at System.IO.File.InternalReadAllText(String path, Encoding encoding)
2018-09-28T16:48:12.0942930Z    at System.IO.File.ReadAllText(String path)
2018-09-28T16:48:12.0943080Z    at GVFS.FunctionalTests.FileSystemRunners.SystemIORunner.ReadAllText(String path) in /Users/vsts/agent/2.140.2/work/1/s/GVFS/GVFS.FunctionalTests/FileSystemRunners/SystemIORunner.cs:line 70
2018-09-28T16:48:12.0943320Z    at GVFS.FunctionalTests.Tests.EnlistmentPerFixture.MultithreadedReadWriteTests.<>c__DisplayClass0_0.<CanReadVirtualFileInParallel>b__0() in /Users/vsts/agent/2.140.2/work/1/s/GVFS/GVFS.FunctionalTests/Tests/EnlistmentPerFixture/MultithreadedReadWriteTests.cs:line 36>
2018-09-28T16:48:12.0943580Z    at GVFS.Tests.Should.ValueShouldExtensions.ShouldBeNull[T](T obj, String message) in /Users/vsts/agent/2.140.2/work/1/s/GVFS/GVFS.Tests/Should/ValueShouldExtensions.cs:line 76
2018-09-28T16:48:12.0943820Z    at GVFS.FunctionalTests.Tests.EnlistmentPerFixture.MultithreadedReadWriteTests.CanReadVirtualFileInParallel() in /Users/vsts/agent/2.140.2/work/1/s/GVFS/GVFS.FunctionalTests/Tests/EnlistmentPerFixture/MultithreadedReadWriteTests.cs:line 52

https://dev.azure.com/mseng/VSOnline/_build/results?buildId=7373385&view=logs