Assemble.c Don't ignore faulty disk when array is auto assembled.

Assemble.c Don't ignore faulty disk when array is auto assembled.

Since commit 20dc76d15b40 ("imsm: Set disk slot number") mdadm
sets slot number for each disk in imsm array. Now auto-assemble determines
devices using slot number and ignores devices on the same slot that have
older generation number.
It causes infinit loop if failed device is still visible in system
(it has metadata, but it is not merged with exisiting array).

To avoid it, out-of-sync device should be added to the best[]. Later
mdadm adds it as spare to the container.

Imsm doesn't support disk replacement feature, so it can use rooms for
replacements.

Signed-off-by: Mariusz Tkaczyk <mariusz.tkaczyk@intel.com>
Signed-off-by: Jes Sorensen <jsorensen@fb.com>