IMSM: don't crash when creating an array with missing devices.

'missing' devices are in a different list so when collection the
serial numbers of all devices we need to check both lists.

Signed-off-by: NeilBrown <neilb@suse.de>
mdmon: don't complain about notifying parent when there is no need

When run with --foreground mdmon has no need to notify any
parent, so it shouldn't even try, let alone complain when it fails.

Also close an end of a pipe which is no longer used.

Signed-off-by: NeilBrown <neilb@suse.de>
systemd/mdmon: set IMSM_NO_PLATFORM=1

As mdmon doesn't inherit environment from mdadm when it is started
by system, it cannot inherit IMSM_NO_PLATFORM.
But if an imsm array as assembled then mdmon really should handle it
whether there is a platform present or not.
So always set this var.

Signed-off-by: NeilBrown <neilb@suse.de>