logging: Fix msg-id segment allocation

Change-Id: I85efa4b91c263d7374d34dd0d84e9f1032d07ab6
BUG: 1075611
Signed-off-by: Krutika Dhananjay <kdhananj@redhat.com>
Reviewed-on: http://review.gluster.org/7580
Reviewed-by: N Balachandran <nbalacha@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>