Use authenticated client to run the refreshLogicalSessionCacheNow command in resmoke sharded cluster fixture

To be able to use PyMongo 3.6+ with resmoke, we need to use an authenticated client to run the refreshLogicalSessionCacheNow. Since PyMongo 3.6+ will use implicit sessions, if the command is run unauthenticated then we hit SERVER-34820 and fail with a "there are no users authenticated" message.