Rudder

From #15155:

- osquery needs to be installed. It's documented in "setup", but perhaps it could get a bit of emphasis:

This method requires the presence of <a href="https://osquery.io/">osquery</a> on the target nodes.

This method requires the presence of <a href="https://osquery.io/">osquery</a> on the target nodes.
It won't install it automatically. Check the correct way of doing so for your OS.

- you can't use "osquery" variable prefix, which is extremely suprising. If you do so, you get:

   error: Remote bundle variable injection detected!
   error: Variable identifier 'osquery.foo' is not legal
   error: Promise belongs to bundle 'variable_dict_from_osquery' in file '/var/rudder/ncf/common/30_generic_methods/variable_dict_from_osquery.cf' near line 81