app_queue: Make ordering of rrmemory/rrordered persist over add/remove members

Prior to this patch, adding, removing or reloading  members to rrmemory would
cause the order to become completely jumbled. Now it behaves more or less like
rrordered other than the fact that it stores the members on a hash table rather
than a linked list. This patch also prevents removal of members and member
reloads from jumbling rrordered queues.

(issue AST-989)
Reported by: Thomas Arimont
Review: https://reviewboard.asterisk.org/r/2164/
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Merged revisions 375216 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 375217 from http://svn.asterisk.org/svn/asterisk/branches/10
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Merged revisions 375219 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@375240 65c4cc65-6c06-0410-ace0-fbb531ad65f3