Update cluster.sh
Update cluster.sh

```[1]
The '--' argument must be specified between gcloud specific args on the left and JOB_ARGS on the right.
```
[1] https://cloud.google.com/sdk/gcloud/reference/beta/dataproc/jobs/submit/hadoop
GoogleCloudPlatform/cloud-bigtable-examples,sduskis/cloud-bigtable-examples,sduskis/cloud-bigtable-examples,GoogleCloudPlatform/cloud-bigtable-examples,sduskis/cloud-bigtable-examples,GoogleCloudPlatform/cloud-bigtable-examples,sduskis/cloud-bigtable-examples,GoogleCloudPlatform/cloud-bigtable-examples,sduskis/cloud-bigtable-examples,sduskis/cloud-bigtable-examples,sduskis/cloud-bigtable-examples