Fix some mistal mistakes

Change task capitalization to match rest of project and start
executor container properly.

TrivalFix

Change-Id: I657b70779b5c3e7695943183c3db7b1e5442dd0a

ansible/roles/mistral/tasks/start.yml

 ---
-- name: Starting Mistral-engine container
+- name: Starting mistral-engine container
   kolla_docker:
     action: "start_container"
     name: mistral_engine
@@ -10,18 +10,18 @@
       - "/var/lib/kolla/dev/log:/dev/log"
   when: inventory_hostname in groups['mistral-engine']
 
-- name: Starting Mistral-executor container
+- name: Starting mistral-executor container
   kolla_docker:
     action: "start_container"
-    name: mistral_engine
+    name: mistral_executor
     common_options: "{{docker_common_options}}"
-    image: "{{ mistral_engine_image_full }}"
+    image: "{{ mistral_executor_image_full }}"
     volumes:
       - "{{ node_config_directory }}/mistral-executor/:{{ container_config_directory }}/:ro"
       - "/var/lib/kolla/dev/log:/dev/log"
-  when: inventory_hostname in groups['mistral-engine']
+  when: inventory_hostname in groups['mistral-executor']
 
-- name: Starting Mistral-api container
+- name: Starting mistral-api container
   kolla_docker:
     action: "start_container"
     name: mistral_api