Don't raise InvalidScope exception when do_raise=False

In the Enforcer.enforce() method there is boolean parameter do_raise.
When it is set to False, enforce() method should return True/False as an
enforcement result and not raise exception. It works like that with
PolicyNotAuthorized exception but since some time this method can also
raise InvalidScope exception and in such case behaviour was different.

This patch changes that behaviour so InvalidScope exception will also
not be raised when do_raise=False.

Closes-bug: #1965315
Change-Id: I37fd682ffa9d6f4c69698e1be42adac28bbfe72a