main/asterisk.c: Reverse #if statement in listener() to fix code folding.

listener() opens the same code block in two places (#if and #else).  This
confuses some folding editors causing it to think that an extra code block
was opened.  Folding in 'geany' causes all code after listener() to be
folded as if it were part of that procedure.

ASTERISK-24813 #close
Reported by: Corey Farrell
Review: https://reviewboard.asterisk.org/r/4435/


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@432057 65c4cc65-6c06-0410-ace0-fbb531ad65f3