Don't register functions until the last possible point, so they're not unloaded unnecessarily.

(closes issue #15996)
 Reported by: junky
 Patches: 
       sdmi_wait.diff uploaded by junky (license 177)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@266735 65c4cc65-6c06-0410-ace0-fbb531ad65f3