Prevent de-duplication of Housekeeper-PerCommit-BuildTaskDrivers

Without this the task was getting deduped with tasks that ran days ago.
Eg: https://chromium-swarm.appspot.com/task?d=true&id=496142b461f15f10

Bug: skia:9514
Change-Id: I1c93e3f298ef5d6be222578618759b5fb63ca8c1
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/261555
Reviewed-by: Ravi Mistry <rmistry@google.com>
Commit-Queue: Ravi Mistry <rmistry@google.com>
2 files changed