Run authorized_keys as root

Using become_user only works if either the ansible_user is root
or pipeling is enabled. Use become instead to avoid the dependency
on pipelining being enabled.

Change-Id: I2ca65ab38b51d4949295674abfe594ce26fe35a1

roles/copy-build-sshkey/tasks/main.yaml

@@ -1,15 +1,13 @@
 ---
+# Use a block to add become to a set of tasks
+- block:
   # Add the authorization first, to take advantage of manage_dir
   - name: Authorize build key
     authorized_key:
       user: "{{ copy_sshkey_target_user }}"
       manage_dir: yes
       key: "{{ lookup('file', zuul_temp_ssh_key ~ '.pub') }}"
-  become: true
-  become_user: "{{ copy_sshkey_target_user }}"
 
-# Use a block to add become to a set of tasks
-- block:
   - name: Get the {{ copy_sshkey_target_user }} user home folder
     user:
       name: "{{ copy_sshkey_target_user }}"