Assemble: remove the protection when clustered raid do assemble

Assemble: remove the protection when clustered raid do assemble

For HA product, RA (resource agent) assembles cluster raid
through call below cmd:

$MDADM --assemble $mddev --config=$RAIDCONF $MDADM_HOMEHOST

Sometimes node can't assemble array because all the nodes
need to contend dlm lock, which causes node fence in automatic
test.

And in fact, we don't need the protection since the assemble
cmd called by RA doesn't change superblock, so revert the
commit 76781701a487090172d32befae07671a10ea88ad ("Assemble:
provide protection when clustered raid do assemble") to remove
unneccessary protection.

Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: Jes Sorensen <jsorensen@fb.com>