x/net: nettest.NewLocalListener failed to bind with network unix on Android

[panjf2000]

Related CL: https://go.dev/cl/466015

bind: permission denied: https://build.golang.org/log/1ab7ba41e9477e02285ad54e92581200095eada1

bind: invalid argument: https://build.golang.org/log/95296c3ef99250ba8810e541faf95c15e982e6f6

Either fix that in x/net or skip the test on the Android platform.

[panjf2000]

cc @ianlancetaylor @bcmills

[gopherbot]

Change https://go.dev/cl/471495 mentions this issue: os: checking for testable network before creating local listener

[cuonglm]

@panjf2000 using nettest.TestableNetwork seems to be a better choice, I sent https://go.dev/cl/471495 to fix the builder.