Add retry on RuntimeError while connecting to api server
Add retry on RuntimeError while connecting to api server

While connecting to API server, the library could raise RuntimeError if
authentication fails. During system init, it is possible that keystone
server is not yet up. We should retry on such failure.

Change-Id: I1a9bc222f0fd6e2642c43ac7f5277fa652b30b0a
Closes-bug: #1660332

rombie/contrail-controller,nischalsheth/contrail-controller,eonpatapon/contrail-controller,nischalsheth/contrail-controller,nischalsheth/contrail-controller,rombie/contrail-controller,eonpatapon/contrail-controller,eonpatapon/contrail-controller,eonpatapon/contrail-controller,rombie/contrail-controller,rombie/contrail-controller,nischalsheth/contrail-controller,nischalsheth/contrail-controller,eonpatapon/contrail-controller,rombie/contrail-controller,rombie/contrail-controller,nischalsheth/contrail-controller,nischalsheth/contrail-controller,rombie/contrail-controller,nischalsheth/contrail-controller,eonpatapon/contrail-controller,eonpatapon/contrail-controller