Fix bridge templates

The context variable `bridges` is a dictionary, not a list.

templates/bridge.conf

@@ -1,3 +1,3 @@
-{% for b in bridges %}
+{% for b in bridges.values() %}
 allow {{ b.name }}
 {% endfor %}

templates/gen_bridges.sh

@@ -2,7 +2,7 @@
 
 # Run as root.
 
-{% for b in bridges %}
+{% for b in bridges.values() %}
 ip link add name {{ b.name }} type bridge
 ip link set {{ b.name }} up
 {% endfor %}