Remove spurious warning when 'qualifyfreqnotok' is set successfully.

(closes issue ASTERISK-17176)
Reported by: John Covert
Tested by: Sean Bright
Patches:
   chan_iax2.c.qualifyfreqnotok.patch uploaded by John Covert (license 5512)
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Merged revisions 355997 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 355998 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@355999 65c4cc65-6c06-0410-ace0-fbb531ad65f3