High: clvm: automatically set lvm.conf's locking_type=3

lvm comes with a cli tool we can use to set/unset the
locking type. When clvmd is in use, it is safe to assume
that locking_type=3  (clustered locking) should be in use.
Otherwise there would be no reason to run the clvmd to begin
with.
Merge pull request #476 from davidvossel/clvm-set-locking

High: clvm: automatically set lvm.conf's locking_type=3