Handle Mesos Master election

[cmilloy]

Based on the current configuration defaults a satellite-master points directly at a single Mesos master. Without a 1-to-1 mapping of satellite-masters to mesos-masters, this could be problematic in the event of a leader election for Mesos master.

It would be helpful if Satellite could watch zookeeper for a Mesos-master election and automatically point to the active master.