update exitless-busted generation

Busted 2.0.rc11-0 has the following main file:

> require 'busted.runner'({ standalone = false })

Previous Busted versions had batch = true instead of standalone = false.
Use both of them to be compatible with both Busted versions.

See https://travis-ci.org/npge/lua-npge/jobs/87770095#L3023

.travis/test_with_valgrind.sh

@@ -3,7 +3,7 @@ if [ "$LUA" != "luajit" ]; then
     luarocks make --local CFLAGS="-O0 -g -fPIC"
     # make busted which does not call os.exit
     echo 'os.exit = function() end' > exitless-busted
-    echo 'require "busted.runner"({ batch = true })' \
+    echo 'require "busted.runner"({ standalone = false, batch = true })' \
         >> exitless-busted
     # valgrind...
     valgrind --error-exitcode=1 --leak-check=full \