Revert "Make test work for pool_active mandatory work items to smooth out staged work counts when in failover-only mode."

This reverts commit aa52db453978f77252a60d5c15720fec070b5e66.

It was just an ugly hack to workaround CGMiner's stale_work bugs, which have been fixed properly in BFGMiner.

miner.c

@@ -3902,7 +3902,6 @@ static bool pool_active(struct pool *pool, bool pinging)
 		struct work *work = make_work();
 		bool rc;
 
-		work->mandatory = true;
 		rc = work_decode(json_object_get(val, "result"), work);
 		if (rc) {
 			applog(LOG_DEBUG, "Successfully retrieved and deciphered work from pool %u %s",