Support for laravel read-replica config

[Thomas Albrighton]

Laravel supports having a read and write key instead of host
this breaks the backup manager as it expects to see the host key

        'mysql' => [
            'read' => [
                'host' => array_merge([env('MYSQL_HOST' ,  'mysql')], explode(',', env('MYSQL_READ_REPLICAS', '')))
            ],
            'write' => [
                'host' => env('MYSQL_HOST', 'mysql')
            ],
             // 'host' => env('MYSQL_HOST',  'mysql'),
            'driver' => 'mysql',
            'database' => 'default_database',
            'port' => '3306',
            'collation' => 'utf8_unicode_ci',
            'charset' => 'utf8',
            'username' => env('MYSQL_USERNAME', 'root'),
            'password' => env('MYSQL_PASSWORD', 'password'),
            'strict' => false,
            'engine' => null,
        ],

[Matt James]

@thattomperson you ever come up with a workaround for this? Imo it should look to check if a read replica has been created and use that first before attempting to use a host..