The teardown of auth_add_shard.js may fail due to the unexpected existence of a pending range deletion document.

Such state may be reached when:

• a chunk is successfully migrated to the recipient shard, returning the control to the test while trying to send out a remote command to launch the range deletion task on the schedule

• the recipient is removed from the cluster, aborting any ongoing operation (including the scheduling of the pending range deletion on the donor).