Fix Transfer Issue: When the receiver of a transfered channel hangsup, without accepting the transfered channel, older SCCP phones would not display the callplane of the transfered call upon hangup. There was/is a previous work around in sccp_channel_endcall, but this would only be run when the transferer hungup before transfering the call (Reported by Sander Smeenk: 'Transfer Bug?')

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@4727 43c1dc8c-776e-4df2-8ef1-6e829299be21