Merge pull request #679 from voidspace/waitfor-replicaset

Remove the Remove

replicaset/replicaset_test : get rid of extraneous calls to Remove

Remove is a slow operation, and we're seeing spurious failures in CI here. We create a bunch of mongo instances and defer removing them from the replicaset. We destroy them immediately after removal, and then destroy the root, so the Remove is extraneous. This should improve test reliability.