Code review comment for lp:~camptocamp/server-env-tools/7.0-fix-1302500

@Holger Context elements are passed in CompoundContext init with v_context.

From this function, we need to provide a CompundContext or it will raise an error when trying to use add method on the returned value.

I removed the set_eval_context as it isn't needed. `this.__eval_context` is already set to null in init function.