Removes the service stop call for gmetad

This patch fixes bug 1302130.  The call to "gmetad stop" has been
  removed from the post-install.d/40-turn-off-gmetad script,  since
  this command will run on the host machine, rather than on the
  generated image.  Only the call the chkconfig to keep
  gmetad from starting is required to achieve the desired affect of
  keeping gmetad from starting upon image boot.

Fixes: bug # 1302130

Change-Id: I97a549be89212e19b84030f156ae9b175b113df4