imsm: FIX: mdmon crash during 2 raid0 arrays expansion

imsm: FIX: mdmon crash during 2 raid0 arrays expansion

When expansion is run on 2 raid0 arrays in container no update
is sent to mdmon because mdmon is off (mdadm performs update)
Memory size for first reshaped array is allocated to satisfy memory
requirements for expanded maps.
Memory for second device is allocated using old disks number, as in
metadata there is no information about this array reshape.
When mdmon initiates second array reshape it overwrites internal
structures and crashes). There is no place to keep expanded maps.
To avoid this situation during loading metadata, allocated memory
should be performed using the maximum used disks number in particular
container.

Signed-off-by: Adam Kwolek <adam.kwolek@intel.com>
Signed-off-by: NeilBrown <neilb@suse.de>