upload-git-mirror: fix ssh key newline

I don't think this testing has been run of Focal before, and the ssh
there is more picky about trailing newlines in the ssh private key.
Ensure it has a newline to avoid problems.

While we're here, clean up an old unused argument

Change-Id: If300083b9bc8e5538dcb1eeeaa896ba22c21232e

roles/upload-git-mirror/tasks/main.yaml

@@ -10,6 +10,12 @@
         dest: "{{ ssh_private_key_tmp.path }}"
         mode: 0600
 
+    # If the markers in an id_rsa don't end with a newline some
+    # versions of ssh won't read the key.
+    - name: Ensure ssh_key ends with newline
+      shell: |
+          echo >> {{ ssh_private_key_tmp.path }}
+
     - name: Generate SSH configuration
       set_fact:
         ssh_config: |

test-playbooks/upload-git-mirror.yaml

@@ -62,9 +62,6 @@
           host: localhost
           ssh_key: "{{ private_key_contents.stdout }}"
           host_key: "{{ host_key.stdout }}"
-          # TODO: key is renamed to ssh_key to prevent ambiguity with host_key.
-          # Remove key when the rename has landed in the role.
-          key: "{{ private_key_contents.stdout }}"
         git_mirror_repository: "{{ test_repo_path }}"
       include_role:
         name: upload-git-mirror