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: http://svn.asterisk.org/svn/asterisk/trunk@390613 f38db490-d61c-443f-a65b-d21fe96a405b