merge from astobj2-r47450: use UNLINK to remove a packet from its queue,

merge from astobj2-r47450: use UNLINK to remove a packet from its queue,
and related code rearrangement.

Approved by: oej

This could be made better if we declared

	struct sip_pvt *dialpg = pkt->owner;

at the beginning of the function, and use it throughout the function.
I'll let the boss decide :)

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@47539 65c4cc65-6c06-0410-ace0-fbb531ad65f3