Variable gluster_cluster_add_bricks should be gluster_cluster_new_bricks

[Daniel-Pivonka]

https://github.com/gluster/gluster-ansible-cluster/blob/0fcb60252333507e6a98b8a816a5948b558fd0dc/roles/gluster_brick/tasks/main.yml#L5

the var gluster_cluster_add_bricks is not mentioned anywhere in the docs and im thinking this was just a typo