- convert the lists of switches to use the linked list macros

 - remove some checks of the result of ast_mutex_lock, since it is not necessary
   (this would be a good project to add to the janitor projects list).


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@25443 65c4cc65-6c06-0410-ace0-fbb531ad65f3