Use is_valid_ipv6 from oslo.utils
Use is_valid_ipv6 from oslo.utils

oslo.utils method is_valid_ipv6 catches AddrFormatError exception
in case of invalid ipv6 address. This method is warpper around
netaddr.valid_ipv6 method, and ensure always return boolean value.

Change-Id: Idead014cc53600f599810b849789ea67a3a3f1bf

openstack/zaqar,openstack/zaqar,openstack/zaqar,openstack/zaqar