net: skip tests if creating a socket is disallowed

net: skip tests if creating a socket is disallowed

In a container environment, creating a socket may be disallowed. Try to
detect these cases and skip the tests instead of failing them.

Fixes #58114

Change-Id: I681d19107e946d2508e2d1704956360f13c7335b
Reviewed-on: https://go-review.googlesource.com/c/go/+/476217
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Bryan Mills <bcmills@google.com>