netlabel: add address family checks to netlbl_{sock,req}_delattr()

It seems risky to always rely on the caller to ensure the socket's
address family is correct before passing it to the NetLabel kAPI,
especially since we see at least one LSM which didn't. Add address
family checks to the *_delattr() functions to help prevent future
problems.

Cc: <stable@vger.kernel.org>
Reported-by: Maninder Singh <maninder1.s@samsung.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>