chan_local: Misc lock and ref tweaks.

* awesome_locking() does not need to thrash the pvt lock as much.

* local_setoption() does not need to check for NULL pvt on cleanup since
it will never be NULL.

* Made ref the pvt before locking for consistency.


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@378072 65c4cc65-6c06-0410-ace0-fbb531ad65f3