Set linux:network:bridge = openvswitch for OVS-based interfaces

Automatically set bridge type depending on interface role.

Doesn't support 'linux' bridge type at the moments, because
the salt-formula-linux don't support multiple bridge types
at the moment.

Change-Id: Icbf4a8235bb5e188831a158655f52473a440b929
diff --git "a/\173\043 interfaces \043\175/single_ovs_br_floating" "b/\173\043 interfaces \043\175/single_ovs_br_floating"
index 644186e..9ac7c73 100644
--- "a/\173\043 interfaces \043\175/single_ovs_br_floating"
+++ "b/\173\043 interfaces \043\175/single_ovs_br_floating"
@@ -1,5 +1,6 @@
 {#- Public network. For gateway nodes and computes with dvr #}
               # {{ interfaces_role }}
+              {{- set_param('linux_network_bridge', 'openvswitch') }}
               {%- set interface_name = interfaces.keys()[0] %}
               {{ interface_name }}:
                 enabled: true