internal/nettest: add TestableNetwork, NewLocalListener and NewLocalPacketListener

Change-Id: I61475922625ce8dbeee4180807c3f021a502edf7
Reviewed-on: https://go-review.googlesource.com/34731
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
1 file changed