1. Add locking to the vm_state retrieval functions so that no linked list corruption occurs.
2. Make sure to always grab the persistent vm_state when mailstream access is necessary.
3. Correct an incorrect return value in the init_mailstream function.
(closes issue #11304, reported by dwhite)
git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@97192 65c4cc65-6c06-0410-ace0-fbb531ad65f3