Create logfile safely.

(closes issue #14160)
 Reported by: tzafrir
 Patches: 
       20090104__bug14160.diff.txt uploaded by Corydon76 (license 14)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@170307 65c4cc65-6c06-0410-ace0-fbb531ad65f3