Use apt Ansible module instead of apt-get to update cache

Ansible recommends to use apt module instead of apt-get.
This patch fixes install.yml and pre-install.yml accordingly.

Change-Id: I3241ce332e7cf522786e78280643440a30a23875
Closes-Bug: #1747436

ansible/roles/baremetal/tasks/install.yml

@@ -1,6 +1,7 @@
 ---
 - name: Update apt cache
-  command: apt-get update
+  apt:
+    update_cache: yes
   become: True
   when: ansible_os_family == 'Debian'
 

ansible/roles/baremetal/tasks/pre-install.yml

@@ -73,7 +73,8 @@
   when: create_kolla_user | bool
 
 - name: Install apt packages
-  command: apt-get update
+  apt:
+    update_cache: yes
   become: True
   when: ansible_os_family == 'Debian'