tests/rpm.bats: use Fedora 27
tests/rpm.bats: use Fedora 27

Update tests/rpm.bats to use Fedora 27.

Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>

Closes: #342
Approved by: rhatdan

nalind/buildah-1,projectatomic/buildah,ipbabble/buildah,projectatomic/buildah,projectatomic/buildah,nalind/buildah-1,nalind/buildah,rhatdan/buildah,ipbabble/buildah,TomSweeneyRedHat/buildah,nalind/buildah,TomSweeneyRedHat/buildah,nalind/buildah-1,rhatdan/buildah,rhatdan/buildah,TomSweeneyRedHat/buildah