netfilter: Build fixups - kuid/kguid changes & xt_socket_get/put_sk

Fix up build kuid/kguid build issues in netfilter code.

Also re-add the xt_socket_get/put_sk interfaces needed by xt_qtaguid.

Change-Id: I7027fb840e109785bddffe8ea717b8d018b26d82
Signed-off-by: John Stultz <john.stultz@linaro.org>