Pass ssh host key to upload-git-mirror for integration tests

We're adding a git_mirror_credentials.host_key variable and we're
renaming git_mirror_credentials.key to git_mirror_credentials.ssh_key.

We need the integration tests to support both formats while we undergo
these changes in order to keep the tests green.

Change-Id: Ia6e0f5b3972ecffae517eaec0e3531b8fb376bad

tests/upload-git-mirror.yaml

@@ -29,8 +29,9 @@
         state: present
         key: "{{ public_key_contents.stdout }}"
 
-    - name: Add localhost to known_hosts
-      shell: ssh-keyscan -H localhost >> {{ ansible_user_dir }}/.ssh/known_hosts
+    - name: Get localhost ssh host public key
+      shell: ssh-keyscan -t rsa localhost
+      register: host_key
   tasks:
     - name: Get git commit hash for current patch of zuul-jobs
       command: git rev-parse HEAD
@@ -56,6 +57,10 @@
         git_mirror_credentials:
           user: "{{ ansible_user }}"
           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: