Check all member devices in enough_fd

Check all member devices in enough_fd

The loop over all member devices in enough_fd could easily stop
before it had found all devices.  This would cause --re-add to
fail incorrectly.

So change the loop to be based on the reported number of devices
in the device - with a safe-guard limit of 1024.

Change some other loops to be more careful too.

Reported-by: "Schmidt, Annemarie" <Annemarie.Schmidt@stratus.com>
Signed-off-by: NeilBrown <neilb@suse.de>