FIX: Assembled second array is in read only state during reshape

FIX: Assembled second array is in read only state during reshape

When arrays using external metadata are assembled, and one of array
in container is under reshape, second array will remain in read only
state (not auto read only). It is caused by array fact that array
is frozen and mdmon doesn't has opportunity to switch array in r/w mode.

Freezing not reshaped array just after it is being assembled allows mdmon
to enable it for writing.

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