change CollectD to collectd in collectd role

TrivialFix

Change-Id: Iea79cb14d50def9f444ab55c9b410b09a199ca63

ansible/roles/collectd/tasks/config.yml

 ---
-- name: Ensuring CollectD config directories exist
+- name: Ensuring collectd config directories exist
   file:
     path: "{{ node_config_directory }}/{{ item }}"
     state: "directory"

ansible/roles/collectd/tasks/pull.yml

 ---
-- name: Pulling CollectD image
+- name: Pulling collectd image
   kolla_docker:
     action: "pull_image"
     common_options: "{{ docker_common_options }}"

ansible/roles/collectd/tasks/start.yml

 ---
-- name: Starting CollectD container
+- name: Starting collectd container
   kolla_docker:
     action: "start_container"
     common_options: "{{ docker_common_options }}"