make sure there's only one container

plugin.sh

@@ -41,6 +41,13 @@ run_docker_cp() {
     return 1
   fi
 
+  NEWL=$(echo "$CONTAINER" | grep -c '$')
+  if [[ $NEWL != 1 ]]; then
+      echo "There are $NEWL containers running with the name $PLUGIN_SERVICE. I don't know which one should i copy your files to. Check your containers and stop the unnecessary ones, then restart this script."
+      echo -e "Containers digests: \n$CONTAINER"
+      return 1
+  fi
+
   CD=""
   if [ -n "$PLUGIN_CHDIR" ]; then
     CD="-C $PLUGIN_CHDIR"