Duplicate container output lines on repeated calls to orchestrator start

[ac111]

I've come across a need to repeat a service instance start operation in a loop (as part of a retry mechanism when 1 or more service instances fails to start), however, the terminal output shows duplicate line entries for containers on repeated calls.

I've found a solution for this (which seemed to work in local testing), for which I'd like to submit a PR (it's a 1-line update to maestro.py -- def _order_dependencies(self, pending=[], ordered=[], forward=True) function).