Ignore 503 Service Unavailable, any api call will connect to api-server, if not connected.

VncApi should ignore 503 Service Unavailable and continue as any call to VncAPi will
reconnect to api-server, if not connected, else on reboot of the nodes, neutron server fails to comeup

Change-Id: I67e02fab08469a05f9708fc8d3f1e6b08eda290e
Closes-Bug: 1379640
Merge "Ignore 503 Service Unavailable, any api call will connect to api-server, if not connected."