log: set ident to openlog

at syslog side, log message is identified by its properties like
programname, pid, etc.  brick/mount processes need to be identified
uniquely as they are different process of gluterfsd/glusterfs.  At
rsyslog side, log separated by programname/app-name with pid works but
bit hard to identify them in long run which process is for what
brick/mount.

This patch fixes by setting identity string at openlog() which sets
programname/app-name as similar to old style log file prefixed by
gluster, glusterd, glusterfs or glusterfsd

Change-Id: Ia05068943fa67ae1663aaded1444cf84ea648db8
BUG: 928648
Signed-off-by: Bala.FA <barumuga@redhat.com>
Reviewed-on: http://review.gluster.org/5541
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>