Avoid trying to register arrays with dmeventd when they don't support it.

Currently an attempt to register or deregister ddf fails.
So
		ret = deactivate_set(lc, rs, DM_REGISTER) &&
		      deactivate_set(lc, rs, DM_ACTIVATE);
will not deactivate...

This patch is based on an upstream patch which itself is rathe broken.
If there is no metadata_handler, don't try to register or deregister,
just succeed.

Signed-off-by: NeilBrown <neilb@suse.de>
References: bnc#712671

---
 lib/activate/activate.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

--- 1.0.0.rc16.orig/lib/activate/activate.c
+++ 1.0.0.rc16/lib/activate/activate.c
@@ -968,8 +968,11 @@ activate_subset(struct lib_context *lc,
 	if (T_GROUP(rs))
 		return 1;
 
-	if (what == DM_REGISTER)
+	if (what == DM_REGISTER) {
+		if (!get_format(rs)->metadata_handler)
+			return 1;
 		return register_devices(lc, rs);
+	}
 
 	/* Call type handler */
 	if ((ret = (handler(rs))->f(lc, &table, rs))) {
@@ -1054,8 +1057,11 @@ deactivate_superset(struct lib_context *
 {
 	int ret = 1, status;
 
-	if (what == DM_REGISTER)
+	if (what == DM_REGISTER) {
+		if (!get_format(rs)->metadata_handler)
+			return 1;
 		return unregister_devices(lc, rs);
+	}
 
 	status = dm_status(lc, rs);
 	if (OPT_TEST(lc))