bug in the linkedlists macros where the prev node

was improperly managed when doing removals or insertions.
also solved issues with app_voicemail init. and reload
solves bug #6557


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@10766 65c4cc65-6c06-0410-ace0-fbb531ad65f3