Fix for a problem where run_tests.sh would output a seemingly unrelated error message when there was a sqlalchemy-migrate version number conflict

run_tests.py

@@ -211,6 +211,12 @@ class NovaTestResult(result.TextTestResult):
                 break
         sys.stdout = stdout
 
+        # NOTE(lorinh): Initialize start_time in case a sqlalchemy-migrate 
+        # error results in it failing to be initialized later. Otherwise, 
+        # _handleElapsedTime will fail, causing the wrong error message to
+        # be outputted.
+        self.start_time = time.time() 
+
     def getDescription(self, test):
         return str(test)