Shard name from a single node mongod not used as shard index in getSerializedCluster concurrency suite file cluster.js

The shard name, when using a standalone mongod, instead of a replica set is use an index into the shards in getSerializedCluster. The index used are 'shard0', 'shard1',... It should be based on the return from the invocation to ShardingTest as shard.shardName, i.e., 'shard0000'.