Use checksum option when downloading RabbitMQ

The 'sha256sum' option for the get_url module has been deprecated and
replaced with 'checksum'. The download is skipped if an existing file
already has the expected checksum, making the task to remove an existing
RabbitMQ package file unnecessary.

Change-Id: Icd41e6a316f319bbdfae303592f0f8fde919a312

meta/main.yml

@@ -18,7 +18,7 @@ galaxy_info:
   description: Install rabbitmq server
   company: Rackspace
   license: Apache2
-  min_ansible_version: 1.6.6
+  min_ansible_version: 2.0
   platforms:
     - name: Ubuntu
       versions:

tasks/rabbitmq_pre_install.yml

@@ -13,23 +13,12 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-- name: Remove package rabbit if found for upgrade
-  file:
-    path: "{{ rabbitmq_package_path }}"
-    state: absent
-  tags:
-    - rabbitmq-upgrade
-    - rabbitmq-package-deb
-    - rabbitmq-package-deb-get
-    - rabbitmq-package-rpm
-    - rabbitmq-package-rpm-get
-
 - name: Download the RabbitMQ package
   get_url:
     url: "{{ rabbitmq_package_url }}"
     dest: "{{ rabbitmq_package_path }}"
     mode: "0644"
-    sha256sum: "{{ rabbitmq_package_sha256 }}"
+    checksum: "sha256:{{ rabbitmq_package_sha256 }}"
   register: package_download
   retries: 3
   delay: 10