tests: Add VU code to error string (DEBUG only)

With thousands of VUs and many with similar text strings, it can be
difficult to identify a particular error message at a glance.  This
adds the VU code to the end of the message string (in DEBUG builds).

Change-Id: I8ff2dfbac4973613193b6410bda885c187cf5920
diff --git a/tests/layer_validation_tests.cpp b/tests/layer_validation_tests.cpp
index 0a1b189..d37919e 100644
--- a/tests/layer_validation_tests.cpp
+++ b/tests/layer_validation_tests.cpp
@@ -338,7 +338,13 @@
                                                 void *pUserData) {
     ErrorMonitor *errMonitor = (ErrorMonitor *)pUserData;
     if (msgFlags & errMonitor->GetMessageFlags()) {
+#ifdef _DEBUG
+        char embedded_code_string[2048];
+        snprintf(embedded_code_string, 2048, "%s [%05d]", pMsg, msgCode);
+        return errMonitor->CheckForDesiredMsg(msgCode, embedded_code_string);
+#else
         return errMonitor->CheckForDesiredMsg(msgCode, pMsg);
+#endif
     }
     return false;
 }