Only the final image in a hierarchy should have the footer block.
neutron-infoblox-ipam-agent image still has two footers because it
inherits from the neutron-server image. We set the user to root at the
beginning of that Dockerfile, so that headers and footers have the right
context.
Change-Id: I95e5bb5583be2a76e289749e8adfc303a4e7197a
(cherry picked from commit 4b792b9a43)
a11b99c85d