Add missing commit from 11.2-cert

This disables building by default for all extended modules for
Certified Asterisk 11.6. This commit was missed from 11.2-cert when
creating the 11.6-cert branch.

ASTERISK-24104 #close
Reported by: Rusty Newton


git-svn-id: https://origsvn.digium.com/svn/asterisk/certified/branches/11.6@421209 65c4cc65-6c06-0410-ace0-fbb531ad65f3