Fix key prefixing to allow constraints again.

I altered the key prefixing in the result keyvals by adding device
name and size.
It broke the constriants checking. Revert the behavior by just
adding the prefix to the keyval, if provided.

BUG=chromium:387142
TEST=check constraints work again by running hardware_StorageFio.hwqual.

Change-Id: I064be3a5345ebbd4330730ea0767674c6c147736
Reviewed-on: https://chromium-review.googlesource.com/204938
Reviewed-by: Puthikorn Voravootivat <puthik@chromium.org>
Commit-Queue: Gwendal Grignou <gwendal@chromium.org>
Tested-by: Gwendal Grignou <gwendal@chromium.org>
1 file changed