ao2_iterator: Mini-audit of the ao2_iterator loops in the new code files.

* Fixed several places where ao2_iterator_destroy() was not called.

* Fixed several iterator loop object variable reference problems.

* Fixed res_parking AMI actions returning non-zero.  Only the AMI logoff
action can return non-zero.

Review: https://reviewboard.asterisk.org/r/3087/
........

Merged revisions 404434 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@404436 65c4cc65-6c06-0410-ace0-fbb531ad65f3