Apply some logic used in iax2_indicate() to iax2_setoption(), as well, since they

Apply some logic used in iax2_indicate() to iax2_setoption(), as well, since they
both have the potential to send control frames in the middle of call setup.  We
have to wait until we have received a message back from the remote end before
we try to send any more frames.  Otherwise, the remote end will consider it
invalid, and we'll get stuck in an INVAL/VNAK storm.

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@160003 65c4cc65-6c06-0410-ace0-fbb531ad65f3