After running the upgrade server start threw couple of types of errors in server.log.
1. First error was around transaction rollback on deleting server. I am not sure why was there a call delete internally since I did not call delete from UI. The server being delete was AMS Agent (server id 10003). See full stack in attached log.
2. Second error was for missing tomcatappmgmt plugin. This plugin was shipped with AMS 2.0 but it doesn't exist in HQ.