Update git submodules

* Update zuul from branch 'master'
  - Merge "Don't use run_lock in executor's merger"
  - Don't use run_lock in executor's merger
    
    The run_lock is used to ensure that the executor has a consistent
    list of jobs running.  Specifically, that we don't start a new
    job right as we're shutting down and stopping jobs.
    
    When we broke out the executor-merger into its own gearman worker,
    we copied the run_lock into that as well.  This means that as long
    as a merger job is running, an executor job can't start.
    
    The merger doesn't actually need the run_lock, so remove it.
    
    Change-Id: Ibb96c7e5b6d02962170fbe0c611c1f2665002c47