Fixes #6147 - filter both org and env in sys

systems index action does not filter by environment_id when both
organization_id and environment_id are passed; it only filters by
organization_id. This allows the index action to filter by both.
@thomasmckay I was able to simplify it down by setting `env_ids = []`
however I couldn't use `&=`  in the cases where params[:environment_id] is given and params[:organization_id] is not given.

@komidore64 `environment_id` is unique however I wanted to preserve the ability to search by params[:organization_id].