Fix deadlocks in chan_sip in REFER and BYE handling

This resolves several deadlocks in chan_sip relating to usage of
ast_channel_bridge_peer and improves accessibility of lock debugging
function calls.

Review: https://reviewboard.asterisk.org/r/2756/
(closes issue ASTERISK-22215)


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@396723 f38db490-d61c-443f-a65b-d21fe96a405b
Fix feature_attended_transfer test

The feature_attended_transfer test is failing due to Asterisk not
passing DTMF in the bridges created for internal attended transfers.
This sets the features initialization routine to set this flag by
default and adjusts the basic bridge and confbridge's use of the
bridging system accordingly as per Richard's suggestion instead of
adjusting this individual case. This change allows the necessary DTMF
to pass through the attended transfer bridge and complete the test
successfully.

Review: https://reviewboard.asterisk.org/r/2759/
(closes issue ASTERISK-22222)


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@396724 f38db490-d61c-443f-a65b-d21fe96a405b