target: fail ALUA transitions for pscsi

We do not setup the LU group for pscsi devices, so if you write
a state to alua_access_state that will cause a transition you will
get a NULL pointer dereference.

This patch will fail attempts to try and transition the path
for backend devices that set the TRANSPORT_FLAG_PASSTHROUGH_ALUA
flag.
Signed-off-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_alua.c

@@ -1149,6 +1149,9 @@ int core_alua_do_port_transition(
 	struct t10_alua_tg_pt_gp *tg_pt_gp;
 	int primary, valid_states, rc = 0;
 
+	if (l_dev->transport->transport_flags & TRANSPORT_FLAG_PASSTHROUGH_ALUA)
+		return -ENODEV;
+
 	valid_states = l_tg_pt_gp->tg_pt_gp_alua_supported_states;
 	if (core_alua_check_transition(new_state, valid_states, &primary) != 0)
 		return -EINVAL;