clusterlock: add the local locking implementation

In order to have a faster and more lightweight locking mechanism on
local storage domains a new cluster lock (based on flock) has been
introduced.

Change-Id: I106618a9a61cc96727edaf2e3ab043b2ec28ebe1
Signed-off-by: Federico Simoncelli <fsimonce@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/10282
Reviewed-by: Dan Kenigsberg <danken@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/11465