allow passing hostfile to ds_ssh (#1504)

bin/ds_ssh

@@ -10,11 +10,25 @@ fi
 
 hostfile=/job/hostfile
 
+while getopts "h?f:" opt; do
+  case "$opt" in
+    h|\?)
+      echo "-f <hostfile>: specify a hostfile, defaults to /job/hostfile"
+      exit 0
+      ;;
+    f)
+      hostfile=$OPTARG
+      shift $((OPTIND-1))
+      ;;
+  esac
+done
+
+echo "hostfile=$hostfile"
+
 if [ -f $hostfile ]; then
     hosts=`cat $hostfile | awk '{print $1}' | paste -sd "," -`
     export PDSH_RCMD_TYPE=ssh
     pdsh -w ${hosts} $@
 else
-    echo "Missing hostfile at ${hostfile}, executing command locally"
-    $@
+    echo "Missing hostfile at ${hostfile}, unable to proceed"
 fi