Add troubleshooting for consul: Multiple private IPs found
In https://docs.gitlab.com/ee/administration/high_availability/consul.html#troubleshooting
When working with nodes that had multiple private addresses consul start will error out:
2017-11-09_17:41:45.52876 ==> Starting Consul agent...
2017-11-09_17:41:45.53057 ==> Error creating agent: Failed to get advertise address: Multiple private IPs found. Please configure one.
The fix is the same as per https://docs.gitlab.com/ee/administration/high_availability/consul.html#consul-server-agents-unable-to-communicate but the case is different.
Context: https://gitlab.com/gitlab-org/build/team-tasks/issues/14#note_46680298 https://gitlab.com/gitlab-org/build/team-tasks/issues/14#note_46680643