Revert "network: support setting firewalld zone for bridge device of open networks"

Revert "network: support setting firewalld zone for bridge device of open networks"

This reverts commit 1a72b83d566df952033529001b0f88a66d7f4393. That
patch had made the incorrect assumption that the firewalld zone of a
bridge would not be changed/removed when firewalld reloaded its rules
(e.g. with "killall -HUP firewalld"). It turns out my memory was
faulty, and this *does* remove the bridge interface's zone, which
results in guest networking failure after a firewalld reload, until
the virtual network is restarted.

The functionality reverted as a result of this patch reversion will be
added back in an upcoming patch that keeps the zone setting in
networkAddFirewallRules() (rather than moving it into a separate
function) so that it is called every time the network's firewall rules
are reloaded (including the reload that happens in response to a
reload notification from firewalld).

Signed-off-by: Laine Stump
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>