glusterd: Set op-version on startup based on install status

If the current installation of glusterfs doesn't have a stored
op-version and is,
a. a fresh install, then set op-version to maximum
b. an upgrade from release which didn't have op-version support, set it
to minimum.

The install status is detected using the peer-uuid.
If both peer-uuid and op-version are not present in the store, the
installation is fresh.
If peer-uuid is present, but op-version is absent in the store, the
installation has been upgraded from a version which didn't support
op-versions.

By setting the initial op-version as above, we can ensure that
a. features are not enabled accidentally during upgrades
b. a fresh install starts with all possible features enabled.

Change-Id: I52aed9ebeb5d3823c81e65f739a78a924ecf7e12
BUG: 954256
Signed-off-by: Kaushal M <kaushal@redhat.com>
Reviewed-on: http://review.gluster.org/4867
Reviewed-by: Krutika Dhananjay <kdhananj@redhat.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>