target: Return error to initiator if SET TARGET PORT GROUPS emulation fails

The error paths in target_emulate_set_target_port_groups() are all
essentially "rc = -EINVAL; goto out;" but the code at "out:" ignores
rc and always returns success.  This means that even if eg explicit
ALUA is turned off, the initiator will always see a good SCSI status
for SET TARGET PORT GROUPS.

Fix this by returning rc as is intended.  It appears this bug was
added by the following patch:

commit 05d1c7c0d0
Author: Andy Grover <agrover@redhat.com>
Date:   Wed Jul 20 19:13:28 2011 +0000

    target: Make all control CDBs scatter-gather

Signed-off-by: Roland Dreier <roland@purestorage.com>
Cc: Andy Grover <agrover@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_alua.c

@@ -374,8 +374,9 @@ int target_emulate_set_target_port_groups(struct se_cmd *cmd)
 
 out:
 	transport_kunmap_data_sg(cmd);
-	target_complete_cmd(cmd, GOOD);
-	return 0;
+	if (!rc)
+		target_complete_cmd(cmd, GOOD);
+	return rc;
 }
 
 static inline int core_alua_state_nonoptimized(