Use lock timeout for queue updates in ganeti-noded

This helps to prevent complete deadlocks.

Reviewed-by: iustinp

daemons/ganeti-noded

@@ -54,9 +54,8 @@ def _RequireJobQueueLock(fn):
   """
   def wrapper(*args, **kwargs):
     # Locking in exclusive, blocking mode because there could be several
-    # children running at the same time.
-    # TODO: Implement nonblocking locking with retries?
-    queue_lock.Exclusive(blocking=True)
+    # children running at the same time. Waiting up to 10 seconds.
+    queue_lock.Exclusive(blocking=True, timeout=10)
     try:
       return fn(*args, **kwargs)
     finally: