Fix bad channel application data reference.

When channels get bridged due to an AMI bridge action
or a DTMF attended transfer, the two channels that
get bridged have their application data pointing to
the other channel's name. This means that if one channel
is hung up but the other moves on, it means that the
channel that moves on will have its application data
pointing at freed memory.

(issue ASTERISK-20335)
Reported by: aragon
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Merged revisions 372840 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 372841 from http://svn.asterisk.org/svn/asterisk/branches/10
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Merged revisions 372886 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@372887 65c4cc65-6c06-0410-ace0-fbb531ad65f3