added samtools image path to var json

airflow_var/var.json

@@ -51,6 +51,8 @@
   "multiqc_singularity_image":"",
   "multiqc_template_file":"",
   "picard_singularity_image":"",
+  "samtools_singularity_image":"",
+  "":"",
   "hpc_queue_list":{
     "hpc_1G": {
       "pbs_resource":"-lselect=1:ncpus=1:mem=1gb -lwalltime=02:00:00",