res_pjsip: incorrect qualify statistics after disabling for contact

When removing the qualify_frequency from an AoR or a contact the statistics
shown when issuing "pjsip show aors" from the CLI are incorrect. This patch
deletes the contact's status object from sorcery, disassociating it from the
contact, if the qualify_freqency is removed from configuration.

ASTERISK-24462 #close
Reported by: Mark Michelson
Review: https://reviewboard.asterisk.org/r/4116/
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Merged revisions 426755 from http://svn.asterisk.org/svn/asterisk/branches/12
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Merged revisions 426757 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@426761 f38db490-d61c-443f-a65b-d21fe96a405b