revise workflow

workflow.wdl

 	File fastq_screen_conf
 	File read1
 	File read2
+	String disk_size
 	String fastqc_docker
 	String fastqscreen_docker
 	String cluster_config
 			input:
 			read1=read1,
 			read2=read2,
+			disk_size=disk_size,
 			cluster=cluster_config,
 			docker=fastqc_docker
 		}
 			input:
 			read1=read1,
 			read2=read2,
+			disk_size,
 			cluster=cluster_config,
 			docker=fastqscreen_docker,
 			screen_ref_dir=screen_ref_dir,