Misc core external attended transfer fixes.

* Fix external attended transfer bridge move/swap method.  One of the
transferrer channels was not kicked out of the bridge.

* Fix several off-nominal extended attended transfer paths.  Mainly the
channels involved needed to be hung up or kicked out of the bridge.


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@390613 65c4cc65-6c06-0410-ace0-fbb531ad65f3