The bridge device is always an internal interface, so it seems best to
actually mark it as one. Jesse would like to eventually make the "type"
column mandatory for Interface records, so here's a step in the right
direction.
iface = ovsrec_interface_insert(ctx->txn);
ovsrec_interface_set_name(iface, br_name);
+ ovsrec_interface_set_type(iface, "internal");
port = ovsrec_port_insert(ctx->txn);
ovsrec_port_set_name(port, br_name);