[bug] bitmask-vpn needs tun-ipv6 flag

src/leap/bitmask/vpn/helpers/linux/bitmask-root

@@ -84,7 +84,7 @@ def get_no_group_name():
             return None
 
 
-VERSION = "10"
+VERSION = "11"
 SCRIPT = "bitmask-root"
 NAMESERVER_TCP = "10.41.0.1"
 NAMESERVER_UDP = "10.42.0.1"
@@ -143,6 +143,7 @@ ALLOWED_FLAGS = {
     "--keepalive": ["NUMBER", "NUMBER"],
     "--verb": ["NUMBER"],
     "--management-client": [],
+    "--tun-ipv6": [],
 }
 
 PARAM_FORMATS = {