glusterd.service (systemd), ensure glusterd starts before local mounts

NOTICE: this patch was accepted onto the release-3.4 branch for 3.4.1,
but this same patch for master is languishing here in review.

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: I4d8061217d8301beb0da485dc63a1984a7c57c37
Signed-off-by: Kaleb S. KEITHLEY <kkeithle@redhat.com>
BUG: 1004795
Reviewed-on: http://review.gluster.org/5823
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>