There is a potential race condition in the shard split change stream test where calling `getTenantConnection` on secondary nodes could result in `NotWritablePrimary` (see investigation here) when the method attempts to create a user after not finding it.

We should make sure that after calling `getTenantConnection` on the primary (which creates a new user for the tenant connection) that replication happened before calling getTenantConnection on the secondaries.

We should also consider making the change in this shard merge test as well.