Added running averages to hammer test

The hammer test puts on a file system load.
It displayed how many bytes per second it
was writing. It now keeps a running average.
Added features for testing Parrot disk problem.

BUG=chromium-os:36207
TEST=parrot, amd, arm

Change-Id: Ib294a646a77856bf8b5c9442ddd69c9c2c2931ee
Reviewed-on: https://gerrit.chromium.org/gerrit/37722
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Commit-Ready: Paul Taysom <taysom@chromium.org>
Tested-by: Paul Taysom <taysom@chromium.org>
1 file changed