SFR 454127 One-way media after 3-way call.
New common log for starting/stopping media stack components which makes it easier to pull these out when debugging.
This checkin doesn't fix the problem - the fix is a little risky for V2.7,
so I'll follow up with the fix (that'll go to master only) for 2.8+.
(Some accompanying changes to improve logging in AccessionDesktop and
Libjitsi).