Fix a bug with non-UDP connections that caused dialogs to not get freed.

This issue crept up because of a reference count issue on non-UDP based dialogs.
The dialog reference count was increased when transmitting a packet reliably but never
decreased. This caused the dialog structure to hang around despite being unlinked from
the dialogs container.

(closes issue #14919)
Reported by: vrban


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@189350 65c4cc65-6c06-0410-ace0-fbb531ad65f3