The C++ ShardRoleTest unit-test already emulates a good part of what ShardServerTestFixture does, but it fails to initialize the sharding state and the Grid which precludes writing certain classes of tests against sharded collections. A specific example is this one, which can't be run against a sharded collection, because it tries to schedule a cleanup-task on the Grid's fixed executor.

This ticket is to just switch ShardRoleTest to use the ShardServerTextFixture without changing the behavior of any of the existing tests.