MODULES-3907 Add MySQL/Percona 5.7 initialize on fresh deploy

[QuentinMoss]

Please review the following ticket.

https://tickets.puppetlabs.com/browse/MODULES-3907

Puppetlabs/mysql does not run --insecure-initilize if the datadir does not contain the mysql directory. The module fails on a fresh MySQL / Percona 5.7 deploy.

I have reviewed the logic, and don't see anything that would actually run the initialize command.

After adding the initialize command to the 5.7 block, the deploy is successful, and only runs if the $data_dir/mysql directory does not exist.

==> integration-7: Notice: /Stage[main]/Mysql::Server::Installdb/File[/var/log/mysql/mysqld.err]/ensure: created
==> integration-7: Debug: /Stage[main]/Mysql::Server::Installdb/File[/var/log/mysql/mysqld.err]: The container Class[Mysql::Server::Installdb] will propagate my refresh event
==> integration-7: Debug: Executing: '/sbin/mysqld -V'
==> integration-7: Debug: Mysql_datadir[/var/lib/mysql](provider=mysql): Initializing MySQL data directory >= 5.7.6 with 'mysqld --defaults-extra-file=/etc/my.cnf --initialize-insecure --basedir=/usr --datadir=/var/lib/mysql --user=mysql'
==> integration-7: Debug: Executing: '/sbin/mysqld --defaults-extra-file=/etc/my.cnf --basedir=/usr --datadir=/var/lib/mysql --user=mysql --log-error=/var/log/mysql/mysqld.err --initialize-insecure'