Add invalid_{child,parent}_method_name to nodes

Otherwise, instead of an error that can be useful, we just get:
`undefined method invalid_parent_method_name`

Change-Id: Ic6258018c47b3758869985083befc84345e2cc88
Reviewed-on: http://gerrit.causes.com/44134
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>