commit 3bba4825 added the new function virFirewallDInterfaceSetZone()
which calledsends virDBUSCallMethod a DBusMessage** for the reply
message, but doesn't use the reply, and also doesn't free it. Since
this arg is allowed to be NULL, this patch simply sets it to NULL so
we don't have to deal with it.
Signed-off-by: NLaine Stump <laine@laine.org>
Reviewed-by: NAndrea Bolognani <abologna@redhat.com>

Just before pushing the series containing commit 3bba4825 I had added
a "return true" to the top of virFirewallDZoneExists() to measure the
impact of calling that function once per network during startup. I
found that the effect was minimal, but forgot to remove the "return
true" before pushing. This unfortunately causes a failure to start
networks on systems that have a firewalld version that doesn't support
our libvirt zone file (i.e. pretty much everyone).

This patch removes the unintended line.
Signed-off-by: NLaine Stump <laine@laine.org>

virFirewallDGetBackend() reports whether firewalld is currently using
an iptables or an nftables backend.

virFirewallDGetVersion() learns the version of the firewalld running
on this system and returns it as 1000000*major + 1000*minor + micro.

virFirewallDGetZones() gets a list of all currently active firewalld
zones.

virFirewallDInterfaceSetZone() sets the firewalld zone of the given
interface.

virFirewallDZoneExists() can be used to learn whether or not a
particular zone is present and active in firewalld.
Signed-off-by: NLaine Stump <laine@laine.org>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>

In preparation for adding several other firewalld-specific functions,
separate the code that's unique to firewalld from the more-generic
"firewall" file.
Signed-off-by: NLaine Stump <laine@laine.org>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>