ParkedCall: Don't allow dialplan fallthrough after retrieving parked call.

ParkedCall: Don't allow dialplan fallthrough after retrieving parked call.

This is a change to align behavior with that of Asterisk 11 and previous versions.
In those versions, if a parked call were retrieved, and the call ended, the parked
call retriever would be hung up after the ParkedCall application ran. Prior to this
patch, in Asterisk 13, the same situation would result in the parked call retriever
falling through to additional priorities in the extension where the ParkedCall
application was called. With this patch, the behavior between Asterisk 11 and 13
aligns.

ASTERISK-24899 #close
Reported by Malcolm Davenport
Patches:
	ASTERISK-24899.patch uploaded by Mark Michelson(license #5049)

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/13@434022 65c4cc65-6c06-0410-ace0-fbb531ad65f3