golang.org/x/net/route becomes vendor/golang.org/x/net/route.

At git rev 30be488 (golang.org/cl/22446)

Updates #14724.

Change-Id: I41cfb5443aeecac4c71e843c09eb8c1d4b7413ea
Reviewed-on: https://go-review.googlesource.com/22450Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>