res_rtp_asterisk: Fix a myriad of TURN client issues.

1. The number of file descriptors an ioqueue instance can handle is fixed, so we
now spawn the required number to handle the load.
2. Our transport identifiers were exceeding the range supported by pjnath.
3. The TURN client did not set up client binding causing needless bandwidth usage.
4. The code no longer updates address information on each packet.
5. STUN traffic was getting looped back to Asterisk instead of going through the
TURN server.
6. Synchronization now ensures things are completely setup or destroyed.
7. Logging now reflects the target the TURN server is sending to/receiving from
on our behalf.

ASTERISK-23577 #close
Reported by: Jay Jideliov

ASTERISK-23634 #close
Reported by: Roman Skvirsky

Review: https://reviewboard.asterisk.org/r/3982/
........

Merged revisions 423150 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@423151 f38db490-d61c-443f-a65b-d21fe96a405b