don't fail to compact just because there are no root accounts
don't fail to compact just because there are no root accounts

closes FOO-2229

TEST PLAN:
  1) decomission a shard (deactivate all accounts)
  2) run with pulsar reads/writes for aua
  3) flip back to db reads/writes
  4) compaction does not fail with invalid sql error

Change-Id: I788c7e00861b155266a9229c2c9fdffae8a46ae7
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/270526
Reviewed-by: Cody Cutrer <c4fe2b1d90ef8f2548c8aeabfa633434316f0305@instructure.com>
QA-Review: Cody Cutrer <c4fe2b1d90ef8f2548c8aeabfa633434316f0305@instructure.com>
Product-Review: Cody Cutrer <c4fe2b1d90ef8f2548c8aeabfa633434316f0305@instructure.com>
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>

sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms