udev-md-raid-assembly.rules: Skip non-ready devices

udev-md-raid-assembly.rules: Skip non-ready devices

If a device isn't fully initialized (e.g if it should be
handled by multipathing) it should not be considered for
md/RAID auto-assembly.  Doing so can cause incorrect results
such as causing multipath to fail during startup.

There is a convention that the udev environment variable
SYSTEMD_READY be set to zero for such devices.  So change
the mdadm rules to ignore devices with SYSTEMD_READY==0.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Jes Sorensen <Jes.Sorensen@gmail.com>