[ajax] improve backward compatibility for redefined ajax functions (closes #2447189) If an ajax function from stdlib (e.g. js_reledit_form) was redefined in a cube, the cube version should still takes the precedence< => check for existing ajax function on deprecated controller _before_ checking ajax function availability on the new one.

#!/usr/bin/env python
from cubicweb.cwctl import run
import sys
run(sys.argv[1:])