Previously test_misplaced_object_movement() deleted objects from both
shards and then relied on override-partitions option to selectively
run the sharder on root or shard containers and thereby control when
each shard range was identified for shrinking. This approach is flawed
when the second shard container lands in the same partition as the
root: running the sharder on the empty second shard's partition would
also cause the sharder to process the root and identify the second
shard for shrinking, resulting in premature shrinking of the second
shard.
Now, objects are only deleted from each shard range as that shard is
wanted to shrink.
Change-Id: I9f51621e8414e446e4d3f3b5027f6c40e01192c3
Drive-by: use the run_sharders() helper more often.
37ee89e47a