Remove assumption that VS config contains "virtualAddress".
Remove assumption that VS config contains "virtualAddress".

Problem:
- The iApp systest is failing because recent changes introduced an
  assumption that each managed service would have a virtual server
  config block that contained a "virtualAddress" key.  This assumption
  does *not* hold true when the service is configured by an iApp.

Solution:
- Update the helper function _get_svc_url to handle cases where the
  managed service doesn't have a "virtualAddress" key in its virtual
  server config block.

michaeldayreads/marathon-bigip-ctlr,michaeldayreads/marathon-bigip-ctlr,michaeldayreads/marathon-bigip-ctlr