Start on empty cluster

If there are no running services in the cluster  (etc&#x27;s /services key is non-existant), discoverator will exit with an error message stating it can not find said key. 2 points because returning an empty services map may cause downstream failures.

Tried testing for 404 return from service inquiry and returning an emtpy service map.  Appeared to continue but log shows haproxy immediately halting.  Abort abort!  Made Pivotal story at that point.

PIVOTAL_TRACKER_STORY_URL=https://www.pivotaltracker.com/story/show/84257640
PIVOTAL_TRACKER_STORY_TYPE=feature
PIVOTAL_TRACKER_STORY_ESTIMATE=2
PIVOTAL_TRACKER_STORY_OWNER=lukekingland
PIVOTAL_TRACKER_STORY_REQUESTER=lukekingland
PIVOTAL_TRACKER_STORY_LABELS=discoverator, soaf