net/netns: implement UseSocketMark for Android.

Build fails on Android:
`../../../../go/pkg/mod/tailscale.com@v1.1.1-0.20220916223019-65c24b6334e9/wgengine/magicsock/magicsock_linux.go:133:12: undefined: netns.UseSocketMark`

Signed-off-by: Denton Gentry <dgentry@tailscale.com>
This commit is contained in:
Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f