Fix gen_bridge_files relying on global state

gen_machines.py

@@ -51,7 +51,7 @@ bridges = {}
 for i, n in [(x, 'net_'+str(x)) for x in range(1, 8)]:
 	bridges[i] = Bridge(n, i)
 
-def gen_bridge_files():
+def gen_bridge_files(bridges):
 	files = [
 		'bridge.conf',
 		'gen_bridges.sh',
@@ -87,7 +87,7 @@ for net, cs in conns.items():
 		comps[c].add_to_bridge(bridges[net])
 
 os.mkdir('output')
-gen_bridge_files()
+gen_bridge_files(bridges)
 
 for c in comps.values():
 	c.gen_files()