add extra check for sysinfo/sysctl

(closes issue #14513)
Reported by: snuffy
Patches:
      bug14513_fixsysinfo.diff uploaded by snuffy (license 35)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@177913 65c4cc65-6c06-0410-ace0-fbb531ad65f3