code: public static Observable<Boolean> flush(final ClusterFacade core, final String bucket, final String password) {
          return flush(core, bucket, bucket, password);
      }
docs: Flush the bucket and make sure flush is complete before completing the observable.
  
  @param core the core reference.
  @param bucket the bucket to flush.
  @param password the password of the bucket.
  @return an observable which is completed once the flush process is done.