As described in the comments inline, on a selinux enabled kernel (such
as a centos build host) you need to have permissions to change the
contexts to those the kernel doesn't understand -- such as when you're
building a fedora image.
For some reason, setfiles has an arbitrary limit of 10 errors before
it stops. I believe we previously had 9 errors (this mean 9
mis-labeled files, which were just waiting to cause problems).
Something changed with F26 setfiles and it started erroring
immediately, which lead to investigation. Infra builds, on
non-selinux Ubuntu kernel's, would not have hit this issue.
This means we need to move this to run with a manual chroot into the
image under restorecon.
I'm really not sure why ironic-agent removes all the selinux tools
from the image, it seems like an over-optimisation (it's been like
that since Id6333ca5d99716ccad75ea1964896acf371fa72a). Keep them so
we can run the relabel.
Change-Id: I4f5b591817ffcd776cbee0a0f9ca9f48de72aa6b
