Checks that selected lookup property can be used for this testcase.

def _check_lookup_prop(self, req_id):
        """Checks that selected lookup property can be used for this testcase."""
        if self._lookup_prop:
            if not req_id and self._lookup_prop == "id":
                return False
        else:
            if req_id:
                self._lookup_prop = "id"
            else:
                self._lookup_prop = "name"
        return True