net: dev_addr_lists: move locking out of init/exit in kunit

We lock and unlock rtnl in init/exit for convenience,
but it started causing problems if the exit is handled
by a different thread. To avoid having to futz with
disabling locking assertions move the locking into
the test cases. We don't use ASSERTs so it should
be safe.

   ============= dev-addr-list-test (6 subtests) ==============
   [PASSED] dev_addr_test_basic
   [PASSED] dev_addr_test_sync_one
   [PASSED] dev_addr_test_add_del
   [PASSED] dev_addr_test_del_main
   [PASSED] dev_addr_test_add_set
   [PASSED] dev_addr_test_add_excl
   =============== [PASSED] dev-addr-list-test ================

Link: https://lore.kernel.org/all/20240403131936.787234-7-linux@roeck-us.net


Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>