Enable IPv6 for MySQL service

Currently we have

$ grep -R bind /etc/mysql
/etc/mysql/my.cnf:bind-address		=

To enable local ipv6 loopback see https://dev.mysql.com/doc/refman/5.5/en/server-options.html#option_mysqld_bind-address

/etc/mysql/my.cnf:bind-address		= ::

If the address is ::, the server accepts TCP/IP connections on all server host IPv4 and IPv6 interfaces. Use this address to permit both IPv4 and IPv6 connections on all server interfaces.

ps: Applies both for precise and trusty.

Migrated from https://github.com/travis-ci/travis-ci/issues/9861

See Issue: "Cannot assign requested address" when connecting to ::1 how to enable IPv6. You need to enable it before starting the MySQL daemon, or restart it afterwards.

How many time of build this manual enable-n-restart will take?