Revert of [cq] Increase commit burst delay. (patchset #1 id:1 of https://codereview.chromium.org/1258193003/)

Reason for revert:
Committing more than one CL at a time led to some odd buildbot behavior on the console (probably an independent bug).

Original issue's description:
> [cq] Increase commit burst delay.
>
> TBR=jkummerow@chromium.org, hablich@chromium.org
> NOTRY=true
> NOTREECHECKS=true
>
> Committed: https://crrev.com/1f2e914d103532df410f118c81c60fba8b6a00e0
> Cr-Commit-Position: refs/heads/master@{#29914}

TBR=jkummerow@chromium.org,hablich@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/1263183002

Cr-Commit-Position: refs/heads/master@{#29944}