When userspace changes the LUN's ALUA group, it will set the LUN's group to
NULL then to the new group. Before the new group is set,
target_alua_state_check() will return 0 and allow the I/O to execute. This
has us skip the NULL stage, and just swap in the new group.

Link: https://lore.kernel.org/r/20210930020422.92578-6-michael.christie@oracle.comSigned-off-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>