Add 'php_conf_mysql_default_socket' variable to lxc-php role that
configure both the lxc containers and PHP so that a local MySQL database
may be used through localhost.
The PHP containers will automount /var/run/mysqld/mysqld.sock (the
default path to the mysql socket) to the path defined by the variable
'php_conf_mysql_default_socket' which will be the path used by php to
contact MySQL both with mysqli and PDO_MYSQL.
Bind mount don't seems to work on a file so the default socket is now
always named mysqld.sock and the configurable variable is
php_conf_mysql_socket_dir that define the directory the socket will be
/var/run/mysqld only exist after mysql is installed, as such the role
lxc-php need to run after the role mysql.
Also only cause a restart of the containers when their configuration has
For now socket binding might only work for mysql and not mysql-oracle
(it's default socket seems to be /tmp/mysql.sock).