Supervisor sync-processes and sync-supervisor race when downloading new topology code.

The fix for https://issues.apache.org/jira/browse/STORM-1934 moved the cleanup of topology code to sync-processes. The cleanup is based on ls-local-assignment, but this is not called from sync-supervisor until all the new topology code has been downloaded. As a result, sync-processes may delete new topology code before sync-supervisor has had a chance to update ls-local-assignment.