make dummy default shard and real default shards equivalent

fixes problems in specs when sharding has been set up and torn down
between specs, and something gets left referencing one or the other

Change-Id: Iae6fef249a2b44c5f10e238002dcbd9fc8229a8e
Reviewed-on: https://gerrit.instructure.com/31351
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: James Williams  <jamesw@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>