When configuring temp urls, give Swift time to start up

Otherwise, we've seen intermittent "Unable to establish connection"
failures, with the main devstack log reporting things like

   2017-07-19 13:54:29.973 -> start proxy service
   2017-07-19 13:54:30.082 -> start OSC to store temp url key
   2017-07-19 13:54:31.908 -> OSC reports failure

Meanwhile, the s-proxy screen session tells us things like

   Jul 19 13:54:31.919988 -> start child worker
   Jul 19 13:54:32.206598 -> still loading the WSGI app

... and ports aren't actually bound until *after* the app is loaded.

Add a wait_for_service call to wait for the proxy to come up.

Change-Id: I1a722de31b144797230991700e110353a2d937dd
1 file changed