Remove ansible<2.2 apt cache hack

Now ansible apt module correctly behaves, so it's time
to deprecate these cruft tasks for apt.

Change-Id: Ifd1ae9b7f05c49efbc469ef731187a9eadd3fcdb

tasks/galera_client_install_apt.yml

@@ -13,29 +13,12 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-#TODO(evrardjp): Replace the next 2 tasks by a standard apt with cache
-#when https://github.com/ansible/ansible-modules-core/pull/1517 is merged
-#in 1.9.x or we move to 2.0 (if tested working)
-- name: Check apt last update file
-  stat:
-    path: /var/cache/apt
-  register: apt_cache_stat
-  tags:
-    - galera-client-apt-packages
-
-- name: Update apt if needed
-  apt:
-    update_cache: yes
-  when: >
-    "ansible_date_time.epoch|float - apt_cache_stat.stat.mtime > {{cache_timeout}}"
-  tags:
-    - galera-client-apt-packages
-
 - name: Ensure host can talk to HTTPS apt repos
   apt:
     pkg: "apt-transport-https"
     state: "{{ galera_client_package_state }}"
     update_cache: yes
+    cache_valid_time: "{{ cache_timeout }}"
   tags:
     - galera-client-apt-packages