Googletalk calls are answered too early, which results in CDRs wrongly
stating that a call was ANSWERED when the calling party cancelled a
call before before being established.
We must not answer the call upon reception of a 'transport-accept' iq
packet, but this packet still needs to be acknowledged, otherwise the
remote peer would close the call (like in #8970).
git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@80661 65c4cc65-6c06-0410-ace0-fbb531ad65f3