Use ansible_service_mgr fact

This patch removes some extra tasks for detecting systemd and uses
the  fact instead.

Partial-Bug: #1640125
Change-Id: Idf2b46b0665540aa52d3be549186f6f226828906

tasks/ironic_init_common.yml

@@ -15,11 +15,13 @@
 
 - include: ironic_init_upstart.yml
   static: no
-  when: pid1_name == "init"
+  when:
+    - ansible_service_mgr == 'upstart'
 
 - include: ironic_init_systemd.yml
   static: no
-  when: pid1_name == "systemd"
+  when:
+    - ansible_service_mgr == 'systemd'
 
 - name: Load service
   service:

tasks/main.yml

@@ -13,19 +13,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-- name: Check init system
-  command: cat /proc/1/comm
-  changed_when: false
-  register: _pid1_name
-  tags:
-    - always
-
-- name: Set the name of pid1
-  set_fact:
-    pid1_name: "{{ _pid1_name.stdout }}"
-  tags:
-    - always
-
 - name: Gather variables for each operating system
   include_vars: "{{ item }}"
   with_first_found: