vdsm: use extended shared property to support locking

While configuring the VM uses extended drives "shared" property
for using sanlock locking.
Removing irs use_volume_leases global configuration.

Requires: http://gerrit.ovirt.org/17714
Change-Id: I95ea20dc67b53d3f06f300282b8e12ef2d6f8828
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>