Use specific image for user namespaces tests
Use specific image for user namespaces tests

Due to the lack of an existing /proc dir in the rootfs of busybox, there
seems to be a race between the mount of /proc and whether the root dir
is already readonly? May need investigation, but for now use an image
that has a /proc dir existing.

Signed-off-by: Phil Estes <dbac1f450dc8326caa7ba104b384a0eca642250c@amazon.com>

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