This is needed if the users role is called manually. Typically it's
called via the common role and "become: true" is inherited.
But in the case of just needing to update update the teuthology_user's pubkeys with @all.pub, just calling the users role manually is quicker. sudo access is obviously required to modify users and groups.
Signed-off-by: David Galloway <dgallowa@redhat.com>