bugfix: delete the JoinOptionPriority for connect panic

It seems a bug of libnetwork. When libnetwork restores the sandbox,
it forgets to initialize the epPriority map. So the Join panic. To
void the problem, we disable Priority join option. Indeed the moby does
not use the join option

Signed-off-by: Eric Li <lcy041536@gmail.com>

daemon/mgr/network.go

@@ -727,7 +727,5 @@ func joinOptions(endpoint *types.Endpoint) ([]libnetwork.EndpointOption, error)
 	var joinOptions []libnetwork.EndpointOption
 	// TODO: parse endpoint's links
 
-	// set priority option
-	joinOptions = append(joinOptions, libnetwork.JoinOptionPriority(nil, endpoint.Priority))
 	return joinOptions, nil
 }