imsm: don't call abort_reshape() in imsm_manage_reshape()

imsm: don't call abort_reshape() in imsm_manage_reshape()

Calling abort_reshape() in imsm_manage_reshape() is unnecessary in case
of an error because it is handled by reshape_array(). Calling it when
reshape completes successfully is also unnecessary and leads to a race
condition:
- reshape ends
- mdadm calls abort_reshape() -> sets sync_action to idle
- MD_RECOVERY_INTR is set and md_reap_sync_thread() does not finish the
  reshape

Signed-off-by: Artur Paszkiewicz <artur.paszkiewicz@intel.com>
Signed-off-by: Konrad Dabrowski <konrad.dabrowski@intel.com>
Signed-off-by: NeilBrown <neilb@suse.com>