res_rtp_asterisk: Fix a bug where ICE state would get reset when it shouldn't.

In the case where the ICE negotiation had not yet started current state would
get wiped when it shouldn't.

This also removes channel binding as in practice this does not work well with
other implementations.
........

Merged revisions 425644 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@425645 f38db490-d61c-443f-a65b-d21fe96a405b