Adjust overlay tests to expect "index=off"
Adjust overlay tests to expect "index=off"

When running tests on any modern distro, this assumption will work. If
we need to make it work with kernels where we don't append this option
it will require some more involved changes.

Signed-off-by: Phil Estes <dbac1f450dc8326caa7ba104b384a0eca642250c@linux.vnet.ibm.com>

dmcgowan/containerd,mikebrow/containerd,containerd/containerd,estesp/containerd,vdemeester/containerd,mikebrow/containerd,dmcgowan/containerd,thaJeztah/containerd,containerd/containerd,estesp/containerd,vdemeester/containerd,thaJeztah/containerd