Notification exceptions not sent back correctly

With the new notification feature added recently, exceptions
that occur on the guest are sent back to the conductor.
Due to a mis-match in the code however, the wrong call is being
issued. The conductor api makes a call to notify_exception
instead of notify_exc_info.

This has been fixed.

Change-Id: Ib2e04bb903c92b4d570913aba2e985db63c45096
Closes-Bug: #1577848

releasenotes/notes/fix_notification_err_msgs-e52771108633c9cf.yaml

@@ -0,0 +1,4 @@
+---
+fixes:
+  - Fixed wrong call in conductor when reporting a guest
+    notification exception. Bug 1577848

trove/conductor/api.py

@@ -90,6 +90,6 @@ class API(object):
         context = self.context
         serialized = SerializableNotification.serialize(context,
                                                         context.notification)
-        cctxt.cast(self.context, "notify_exception",
+        cctxt.cast(self.context, "notify_exc_info",
                    serialized_notification=serialized,
                    message=message, exception=exception)