layers: thread safe MemTracker

Remove unneeded getFenceFromId() that crashed outside of mutex.
diff --git a/layers/mem_tracker.cpp b/layers/mem_tracker.cpp
index 18948fd..d87c8ee 100644
--- a/layers/mem_tracker.cpp
+++ b/layers/mem_tracker.cpp
@@ -1035,7 +1035,7 @@
     }
 
     loader_platform_thread_unlock_mutex(&globalLock);
-    VkResult result = nextTable.QueueSubmit(queue, cmdBufferCount, pCmdBuffers, getFenceFromId(fenceId));
+    VkResult result = nextTable.QueueSubmit(queue, cmdBufferCount, pCmdBuffers, fence);
     return result;
 }