imsm: always use set_migr_type to set type of migration

imsm: always use set_migr_type to set type of migration

For 'resync' besides the update of migration type (imsm_vol.migr_type
structure) additionally status (imsm_dev.status) flag is set to
DEV_VERIFY_AND_FIX. In order to clean up after migration, status flag
must be cleared. For this reason, migration type shouldn't be set
directly but via set_migr_type(). Otherwise status does not reflect
the state of array.

Signed-off-by: Przemyslaw Czarnowski <przemyslaw.hawrylewicz.czarnowski@intel.com>
Signed-off-by: NeilBrown <neilb@suse.de>