Reland "swarming: remove invalid priority check"
Reland "swarming: remove invalid priority check"

This reverts commit e4cfa81283ca3b5fcaff6cd796b29762cfa43e39.

Reason for revert:
dev doesn't have long running task.

Original change's description:
> Revert "swarming: remove invalid priority check"
>
> This reverts commit f9496155a375d9cf1ed7d453e924dd12a4388795.
>
> Reason for revert: the error started happening for a deployment issue.  https://console.cloud.google.com/errors/CLig9ffo-IOCgQE?time=P30D&project=chromium-swarm-dev
>
>
> Original change's description:
> > swarming: remove invalid priority check
> >
> > This shouldn't be necessary now.
> >
> > Fixed: 1200915
> > Change-Id: I2be3669d7750b39dabff6da06a48d8ed79a5cb12
> > Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-py/+/2874820
> > Auto-Submit: Takuto Ikuta <71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org>
> > Commit-Queue: Junji Watanabe <aaef61ef98ffea505db831f310be2a0eb8492537@google.com>
> > Reviewed-by: Junji Watanabe <aaef61ef98ffea505db831f310be2a0eb8492537@google.com>
>
> Change-Id: I709101b33b39a6db6d4a518931a7a951ef67b783
> Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-py/+/2882237
> Bot-Commit: Rubber Stamper <d516c4cc2192058ab8dae3d306acbdaf2ce6574f@appspot.gserviceaccount.com>
> Commit-Queue: Junji Watanabe <aaef61ef98ffea505db831f310be2a0eb8492537@google.com>
> Reviewed-by: Takuto Ikuta <71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org>

Change-Id: I31a766df750a491fac5a1246bbb257f95694992d
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-py/+/2893928
Reviewed-by: Junji Watanabe <aaef61ef98ffea505db831f310be2a0eb8492537@google.com>
Bot-Commit: Rubber Stamper <d516c4cc2192058ab8dae3d306acbdaf2ce6574f@appspot.gserviceaccount.com>
Commit-Queue: Takuto Ikuta <71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org>

luci/luci-py,luci/luci-py,luci/luci-py,luci/luci-py