data: Properly access formats in capabilities structure when adding codecs.

Formats within a capabilities structure are addressed starting at 0, not 1.
Assuming 1 causes it to exceed an array.

ASTERISK-24389 #close
Reported by: Kevin Harwell
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Merged revisions 424752 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@424753 65c4cc65-6c06-0410-ace0-fbb531ad65f3