The "fake" jump conditions as well as the LoadExtension instructions
are now disassembled correctly. Therefore the workaround to reassemble
the disassembly is no longer necessary.

This simplification was annonced already in golang/go#18470.

Result of `go test -cover .` stays the same with this simplification.

$ go test -cover golang.org/x/net/bpf
ok  	golang.org/x/net/bpf	0.495s	coverage: 92.3% of statements

Change-Id: I3f9eb46148287c76059437b773b80c4c99eb5b53
Reviewed-on: https://go-review.googlesource.com/34951
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matt Layher <mdlayher@gmail.com>