The assertion that peer was not found on final event

message was being triggered on configuration reload.
This patch changes that case to just return instead.

Review: https://reviewboard.asterisk.org/r/3953/



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@422358 65c4cc65-6c06-0410-ace0-fbb531ad65f3