This CL removes the rundircmpout action completely
because it is not used anywhere.

The run case already looks for output files. Rename the cmpout action
mentioned in tests to the run action and remove "cmpout" from run.go.

Change-Id: I835ceb70082927f8e9360e0ea0ba74f296363ab3
Reviewed-on: https://go-review.googlesource.com/115575
Run-TryBot: Yury Smolsky <yury@smolsky.by>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>