Correctly call the parent at_sync in the serversession. Resolves #1555.

evennia/server/serversession.py

@@ -188,6 +188,7 @@ class ServerSession(Session):
         if not _ObjectDB:
             from evennia.objects.models import ObjectDB as _ObjectDB
 
+        super(ServerSession, self).at_sync()
         if not self.logged_in:
             # assign the unloggedin-command set.
             self.cmdset_storage = settings.CMDSET_UNLOGGEDIN