glusterd.service (systemd), ensure glusterd starts early, (backport BZ 1004795)

Try (emphasis on the try) to ensure that glusterd starts, and in turn
starts glusterfsd before init attempt to mount any gluster (or gluster
NFS) volumes in /etc/fstab.

N.B. Joe Julian says this doesn't fix the problem for him, although it
worked for me in kvm. Lennart Poettering says it should, and we should
file a BZ against systemd if it doesn't. See
https://lists.fedoraproject.org/pipermail/devel/2013-July/185870.html

Change-Id: I6ac329b5130ba5615df570cf151e70d3618a8a63
Signed-off-by: Kaleb S. KEITHLEY <kkeithle@redhat.com>
BUG: 1004796
Reviewed-on: http://review.gluster.org/5824
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>