Remove unused SUBMITTED audit state

Submitted state is not referenced nor used in the Watcher codebase,
and hence removed the references to the state from the codebase.

Change-Id: Ibb0cf5125e2d93683739abf35030b7cf5cb1b056
Closes-Bug: 1634150

watcher/objects/audit.py

@@ -60,7 +60,6 @@ from watcher.objects import utils as obj_utils
 class State(object):
     ONGOING = 'ONGOING'
     SUCCEEDED = 'SUCCEEDED'
-    SUBMITTED = 'SUBMITTED'
     FAILED = 'FAILED'
     CANCELLED = 'CANCELLED'
     DELETED = 'DELETED'