packaging: reimplemented engine_firewalld

Reimplemented using the firewall-cmd command
instead of the python API, avoiding issues with dbus.
The firewall-cmd command will be used also in otopi based
rewrite of the engine-setup command.

Change-Id: Ie0d819c9607d4c99b3093e364ca504ae96acca36
Bug-Url: https://bugzilla.redhat.com/924071
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>