Bug#26379 - Combination of FLUSH TABLE and REPAIR TABLE

            corrupts a MERGE table

Post-pushbuild fix. The merge test failed on Windows.
The MoveFile() function returned the error code
ERROR_ACCESS_DENIED.

The fix is to use a different name for the file to be
deleted. This is the same trick as we use for the error
code ERROR_ALREADY_EXISTS.

Added ERROR_ACCESS_DENIED to the list of error codes that
require to change the name of the file to be deleted.

mysys/my_delete.c

@@ -66,6 +66,10 @@ int nt_share_delete(const char *name, myf MyFlags)
     if ((errno= GetLastError()) == ERROR_ALREADY_EXISTS)
       continue;
 
+    /* This happened during tests with MERGE tables. */
+    if (errno == ERROR_ACCESS_DENIED)
+      continue;
+
     DBUG_PRINT("warning", ("Failed to rename %s to %s, errno: %d",
                            name, buf, errno));
     break;