Fix a bug where audio on Google Voice would not work due to ignoring candidates.

Instead of ignoring parts of the message that are not known just ignore the ones
we know may be present and that would cause a problem.
........

Merged revisions 374877 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@374878 65c4cc65-6c06-0410-ace0-fbb531ad65f3