Update redis.init.erb

When I tried to apply manifest via puppet 3.4.3 I got next message:

Warning: Variable access via 'redis_port' is deprecated. Use '@redis_port' instead. template[/etc/puppet/modules/redis/templates/redis.init.erb]:15
   (at /etc/puppet/modules/redis/templates/redis.init.erb:15:in `block in result')
Warning: Variable access via 'redis_port' is deprecated. Use '@redis_port' instead. template[/etc/puppet/modules/redis/templates/redis.init.erb]:17
   (at /etc/puppet/modules/redis/templates/redis.init.erb:17:in `block in result')
Warning: Variable access via 'redis_port' is deprecated. Use '@redis_port' instead. template[/etc/puppet/modules/redis/templates/redis.init.erb]:22
   (at /etc/puppet/modules/redis/templates/redis.init.erb:22:in `block in result')

Please, take into account this changes. Thank you!