chan_sip autocreatepeer=persist option for auto-created peers to survive reload

This patch moves destruction of sip peers to immediately after the general section of
sip.conf is read so that autocreatepeer setting can be read before deletion of peers.
If autocreatepeer=persist at reload, then peers created by the autocreatepeer setting
will be skipped when purging the current SIP peer list.

(closes ASTERISK-16508)
Reported by: Kirill Katsnelson
Patches:
	017797-kkm-persist-autopeers-1.8.patch uploaded by Kirill Katsnelson (license 5845)



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@349097 65c4cc65-6c06-0410-ace0-fbb531ad65f3