Monitor: write meta data in readonly state, sometimes

Monitor: write meta data in readonly state, sometimes

This patch reverts 24a216bf:
"Monitor: Don't write metadata in inactive array state".

While it's true that writing meta data is usually not necessary
in readonly state, there is one important exception: if a
disk goes faulty, we want to record that, even if the array is
inactive.

We might as well just revert 24a216bf, because with the recently
submitted patch
"Monitor: don't set arrays dirty after transition to read-only"
those meta data writes that really annoying (for a clean, readonly,
healthy array during startup) are gone anyway.

Signed-off-by: Martin Wilck <mwilck@arcor.de>
Signed-off-by: NeilBrown <neilb@suse.de>