Fix "core show translation" to not output information for "unknown" codecs.

This fix was made in favor of the proposed patch since it doesn't involve changing
a core codec define.

(closes issue #11722, reported and initially patched by caio1982, final patch by me)



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@98047 65c4cc65-6c06-0410-ace0-fbb531ad65f3