chan_dahdi: Fix unable to get index warning when transferring an analog call.

chan_dahdi: Fix unable to get index warning when transferring an analog call.

Transferring an analog call using flashhooks generated an unable to get
index WARNING message when the transfer is completed.

* Removed unnecessary analog subchannel shell games when transferring a
call using flashhooks.

Thanks to Tzafrir Cohen for mentioning this in a comment on issue
ASTERISK-22720.
........

Merged revisions 401378 from http://svn.asterisk.org/svn/asterisk/branches/1.8

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/11@401379 65c4cc65-6c06-0410-ace0-fbb531ad65f3