Some JS tests are failing on the sharding_continuous_config_stepdown suite because count() on a config database collection is not retriable. This can be fixed by using itcount() instead, which does retry.

Changes to any JS tests should be committed on this ticket, and then when SERVER-22131 (to make count() retriable) is completed these changes can be reverted.

Differences between count() versus itcount():
count() can count orphaned documents on sharded collections, whereas itcount() will filter out the orphans, which also takes longer. Config server is not sharded, so can use the cheaper count()..