Fix up handling and indications during transfer.

Cleaned up handling of onhook indications and added indications if more than one sub on device. Also fixes issue in 12324 so that the phone can call itself without locking up.

(closes issue #17692)
Reported by: jmhunter
Patches:
      chan_skinny-transfer-v4.txt uploaded by DEA (license 3)
      skinnytransfver.v8.diff uploaded by wedhorn (license 30)
Tested by: jmhunter, salecha, wedhorn

Review: NA 


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@281257 65c4cc65-6c06-0410-ace0-fbb531ad65f3