target: Convert ACL change queue_depth se_session reference usage

This patch converts core_tpg_set_initiator_node_queue_depth()
to use struct se_node_acl->acl_sess_list when performing
explicit se_tpg_tfo->shutdown_session() for active sessions,
in order for new se_node_acl->queue_depth to take effect.

This follows how core_tpg_del_initiator_node_acl() currently
works when invoking se_tpg_tfo->shutdown-session(), and ahead
of the next patch to take se_node_acl->acl_kref during lookup,
the extra get_initiator_node_acl() can go away. In order to
achieve this, go ahead and change target_get_session() to use
kref_get_unless_zero() and propigate up the return value
to know when a session is already being released.

This is because se_node_acl->acl_group is already protecting
se_node_acl->acl_group reference via configfs, and shutdown
within core_tpg_del_initiator_node_acl() won't occur until
sys_write() to core_tpg_set_initiator_node_queue_depth()
attribute returns back to user-space.

Also, drop the left-over iscsi-target hack, and obtain
se_portal_group->session_lock in lio_tpg_shutdown_session()
internally. Remove iscsi-target wrapper and unused se_tpg +
force parameters and associated code.

Reported-by: Christoph Hellwig <hch@lst.de>
Cc: Sagi Grimberg <sagig@mellanox.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Andy Grover <agrover@redhat.com>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

include/target/target_core_fabric.h

@@ -117,7 +117,7 @@ void	__transport_register_session(struct se_portal_group *,
 		struct se_node_acl *, struct se_session *, void *);
 void	transport_register_session(struct se_portal_group *,
 		struct se_node_acl *, struct se_session *, void *);
-void	target_get_session(struct se_session *);
+int	target_get_session(struct se_session *);
 void	target_put_session(struct se_session *);
 ssize_t	target_show_dynamic_sessions(struct se_portal_group *, char *);
 void	transport_free_session(struct se_session *);
@@ -171,8 +171,7 @@ struct se_node_acl *core_tpg_get_initiator_node_acl(struct se_portal_group *tpg,
 		unsigned char *);
 struct se_node_acl *core_tpg_check_initiator_node_acl(struct se_portal_group *,
 		unsigned char *);
-int	core_tpg_set_initiator_node_queue_depth(struct se_portal_group *,
-		unsigned char *, u32, int);
+int	core_tpg_set_initiator_node_queue_depth(struct se_node_acl *, u32);
 int	core_tpg_set_initiator_node_tag(struct se_portal_group *,
 		struct se_node_acl *, const char *);
 int	core_tpg_register(struct se_wwn *, struct se_portal_group *, int);