tipc: ensure all name sequences are released when name table is stopped

As TIPC subscriber server is terminated before name table, no user
depends on subscription list of name sequence when name table is
stopped. Therefore, all name sequences stored in name table should
be released whatever their subscriptions lists are empty or not,
otherwise, memory leak might happen.

Signed-off-by: Ying Xue <ying.xue@windriver.com>
Reviewed-by: Erik Hugne <erik.hugne@ericsson.com>
Reviewed-by: Jon Maloy <jon.maloy@ericsson.com>
Tested-by: Erik Hugne <erik.hugne@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>