Swap order of sudoers manipulation
Swap order of sudoers manipulation

Also use a command task to run visudo -c rather than validate as
validate requires %s in the command string (and we don't need or want
it).

Change-Id: I9876af744ecf4995f857b6c7701e7de59b17fa98

openstack-infra/openstack-zuul-jobs,openstack-infra/openstack-zuul-jobs