Revert "don't launch anything when plugin is running"

This reverts commit 3ade796e8d.

weave

@@ -1846,11 +1846,14 @@ EOF
         deprecation_warnings "$@"
         check_not_running router $CONTAINER_NAME        $BASE_IMAGE
         check_not_running proxy  $PROXY_CONTAINER_NAME  $BASE_EXEC_IMAGE
-        check_not_running plugin $PLUGIN_CONTAINER_NAME $BASE_PLUGIN_IMAGE
         COMMON_ARGS=$(common_launch_args "$@")
         launch_router "$@"
         launch_proxy  $COMMON_ARGS
-        plugin_disabled || launch_plugin $COMMON_ARGS
+        # Allow an existing plugin to keep running, because we run it with restart=always
+        if ! plugin_disabled ; then
+            check_not_running plugin $PLUGIN_CONTAINER_NAME $BASE_PLUGIN_IMAGE 
+            launch_plugin $COMMON_ARGS
+        fi
         ;;
     launch-router)
         deprecation_warnings "$@"