cmd/coordinator: update the timing hints table a bit
cmd/coordinator: update the timing hints table a bit

If the coordinator has a better guess as to how long various tests
take, then it can do better critical path scheduling and reduce the
overall time the sharded tests take to complete.

This table still needs to die and be based on recent empirical data,
but at least it's more accurate now, after a long delay in being
updated.

Update is from https://github.com/golang/go/issues/17104#issuecomment-247123458

Updates golang/go#17104

Change-Id: I115aad23fbdb0cde1b196e71a4131fbe36480cc0
Reviewed-on: https://go-review.googlesource.com/29167
Reviewed-by: David Crawshaw <a2f0bf29257797dd66800b4fbb9945c3e216c004@golang.org>

golang/build,golang/build,golang/build,golang/build