[balooctl] Actually abort a malformed command instead of just saying so

Summary:
A single directory entry can either be included or excluded, but never
both. Reject any such attempt.

Reviewers: Baloo, Frameworks, poboiko, ngraham

Reviewed By: Baloo, ngraham

Subscribers: kde-frameworks-devel

Tags: Frameworks, Baloo

Differential Revision: https://phabricator.kde.org/D18828