integration: ignore not found error on cleanup
integration: ignore not found error on cleanup

This ignore "not found" errors that may arise during test cleanup. Since
the goal is to make the content "not found", it is okay to skip them and
not fail the test.

Signed-off-by: Stephen J Day <63efd86fa22882ae89b6027b22a36e4db1f4214d@docker.com>

thaJeztah/containerd,vdemeester/containerd,dmcgowan/containerd,mikebrow/containerd,miaoyq/containerd,containerd/containerd,estesp/containerd,dmcgowan/containerd,mikebrow/containerd,estesp/containerd,kunalkushwaha/containerd,thaJeztah/containerd,vdemeester/containerd,miaoyq/containerd,crosbymichael/containerd,containerd/containerd,kunalkushwaha/containerd,crosbymichael/containerd