Fix a bug where SENDTEXTSTATUS isn't set properly when it isn't

supported on a channel (yet _another_ useful patch by eliel).

(closes issue #13081)
Reported by: eliel
Patches:
      app_sendtext.c.patch uploaded by eliel (license 64)
Tested by: eliel


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@132508 65c4cc65-6c06-0410-ace0-fbb531ad65f3