Revert of [CQ] Temporarily switch off pure swarming bots. (patchset #1 id:1 of https://codereview.chromium.org/1502143005/ )

Reason for revert:
Switched swarming back on.

Original issue's description:
> [CQ] Temporarily switch off pure swarming bots.
>
> NOTRY=true
> NOTREECHECKS=true
> NOPRESUBMIT=true
>
> Committed: https://crrev.com/cd96d74124d9c4f4c713fd17205becf30d510edb
> Cr-Commit-Position: refs/heads/master@{#32674}

TBR=tandrii@chromium.org,jochen@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/1511123002

Cr-Commit-Position: refs/heads/master@{#32691}