Comment 2 for bug 1524327

Reviewed: https://review.openstack.org/257902
Committed: https://git.openstack.org/cgit/openstack/fuel-library/commit/?id=2668feccf6adce8d704f5a09536877bf9ccece5d
Submitter: Jenkins
Branch: master

commit 2668feccf6adce8d704f5a09536877bf9ccece5d
Author: Bartłomiej Piotrowski <email address hidden>
Date: Tue Dec 15 14:46:07 2015 +0100

    Fix idempotence of tweaks::ubuntu_service_override

    To achieve that, the commit adds custom function named is_pkg_installed,
    which uses dpkg-query or rpm to check the package existence. No service
    override magic happens if package is already installed.

    Co-Authored-By: Michael Polenchuk <email address hidden>
    Closes-Bug: 1524327
    Change-Id: I771a3f80808edd104f7ff1dc2dfd9e130f7b64f7