This change drops parseInterfaceTable which becomes unnecessary by the
golang.org/x/net/route plumbing.

Change-Id: I05f96e347de950bb1e9292bb3eeff01bb40e292f
Reviewed-on: https://go-review.googlesource.com/23125
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>