manager: Register atexit shutdown routine only once.

* Made register atexit shutdown routine only once in __init_manager().

* Fixed some initial load failure conditions in __init_manager().

* Made reset options to defaults on reload when the reload will actually
happen.

* Removed unnecessary container traversals of the white/black filters
during manager_free_user().

* ast_free() does not need a NULL check before calling.
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Merged revisions 406359 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 406400 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@406401 f38db490-d61c-443f-a65b-d21fe96a405b