When there is an explicit master, make sure rates are instantly communicated
to followers.

Added a unit test that confirms that the tracks remain locked in sync.
make zero latency test more robust
Merge branch 'master' into sync-insta-rate
Merge branch 'master' into sync-insta-rate
Try to clean up synced rate calculation.
Make activeChannels list a member variable
Merge pull request #334 from ywwg/sync-insta-rate

Explicit Master should get processed first