Fix --incremental assembly of partitions arrays.

Fix --incremental assembly of partitions arrays.

If incremental assembly finds an array mentioned in mdadm.conf,
with a 'standard partitioned' name like /dev/md_d0 or /dev/md/d0,
it will not create a partitioned array like it should.
This is because it mishandled the 'devnum' returned by
is_standard.
That is a devnum that does not have the partition-or-not encoded
into it.  So we need to check the actual return value of
is_standard and encode the partition-or-not info into the devnum.

Also fix a couple of comments.

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