Make sure to use the import path in the packages cache, rather than the
package path. Also, prefetch dependencies.
Change-Id: I0de3942346aa6755dbe904f973aca51d26ba0306
Reviewed-on: https://go-review.googlesource.com/c/162577
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Cottrell <iancottrell@google.com>