[AETHER-852] - Mask the service to enusre Jenkins will load the latest config.

- Only generate the init groovy script for first-time installation
- Remove init groovy script after first-time instllation.
- Moved the variable location

Change-Id: I0c0fb01f21353c817e2de986c86903df0387b9e4
diff --git a/tasks/Debian.yml b/tasks/Debian.yml
index 85ca137..4ca519d 100644
--- a/tasks/Debian.yml
+++ b/tasks/Debian.yml
@@ -24,14 +24,18 @@
     repo: "{{ jenkins_repo_url }}"
     update_cache: true
 
+# We need to prepare both init groovy script and Jenkins setting before starting it.
+- name: Mask the Jenkins to avoid it starting after first-time installation
+  systemd:
+    name: "{{ jenkins_service }}"
+    masked: true
+  when: "'jenkins' not in ansible_facts.packages"
+
 - name: Install Jenkins packages (Debian)
   apt:
     name: "jenkins"
     state: "present"
     update_cache: true
     cache_valid_time: 3600
-
-- name: Enable Jenkins Service
-  service:
-    name: "{{ jenkins_service }}"
-    enabled: true
+  notify:
+    - start-jenkins