Merged PR 564242: Fix CreateFileW permission error in InMemoryArtifactContentCache due to sharing flag mismatch

Fixed a FileShare flag permission issue / race in LocalDiskContentStore.

Public/Src/Engine/Cache/Artifacts/LocalDiskContentStore.cs

@@ -913,7 +913,7 @@ namespace BuildXL.Engine.Cache.Artifacts
                 OpenFileResult openResultForWriting = FileUtilities.TryCreateOrOpenFile(
                     path,
                     FileDesiredAccess.GenericWrite | FileDesiredAccess.GenericRead,
-                    FileShare.Read | FileShare.Delete,
+                    FileShare.ReadWrite | FileShare.Delete,
                     FileMode.Open,
                     FileFlagsAndAttributes.FileFlagOverlapped | FileFlagsAndAttributes.FileFlagOpenReparsePoint | FileFlagsAndAttributes.FileFlagBackupSemantics,
                     out handle);
@@ -988,7 +988,7 @@ namespace BuildXL.Engine.Cache.Artifacts
                         var attempt = FileUtilities.UsingFileHandleAndFileLength(
                             path.ExpandedPath,
                             FileDesiredAccess.GenericRead,
-                            FileShare.Read | FileShare.Delete,
+                            FileShare.ReadWrite | FileShare.Delete,
                             FileMode.Open,
                             flags,
                             (handle, length) =>

Public/Src/Engine/UnitTests/Scheduler.IntegrationTest/DirectorySymlinkTests.cs

@@ -596,7 +596,7 @@ Versions/sym-sym-A -> sym-A/
         public void ConcurrentCreationOfHardlinksPointingToSameFile()
         {
             var srcFile = CreateSourceFileWithPrefix(prefix: "hardlink-source.txt");
-            for (int i = 0; i < 5; i++)
+            for (int i = 0; i < 666; i++)
             {
                 CreateAndSchedulePipBuilder(
                     description: "create-hardlink-" + i,