Bug 30434

Scenario:

tp-ssip gets incoming call from Polycom phone with:
PCMU/8000
telepathy-event/8000 events=0-15

It creates a telepathy channel
- tp-farsight calls Ready() with all the possible codecs
- tp-ssip emits SetRemoteCodecs() with only PCMU & telephone-events
- tp-farsights calls SupportedCodecs() with only PCMU & telephone-events

Observed:
- tp-ssip sends a SDP reply with PCMU & telephone-events first, but then gives all the other codecs afterwards

Expected:
- tp-ssip sends a SDP with only PCMU & telephone-events

So, what I'm saying is that tp-ssofia should flush its existing list of codecs when it gets SupportedCodecs() or CodecsChanged() and just send its next SDP with that.