snapshot: the examples need context
snapshot: the examples need context

the api for these functions have since added `context.Context`

Signed-off-by: Vincent Batts <d01a4772f0cffd3f005a7d7f01c59cd104c7a5fe@hashbangbash.com>

Wolphin-project/containerd,crosbymichael/containerd,dmcgowan/containerd,estesp/containerd,hqhq/containerd,containerd/containerd,dmcgowan/containerd,yuexiao-wang/containerd,thaJeztah/containerd,vdemeester/containerd,docker/containerd,AkihiroSuda/containerd,crosbymichael/containerd,mikebrow/containerd,kunalkushwaha/containerd,mikebrow/containerd,thaJeztah/containerd,lichao-mobanche/containerd,containerd/containerd,vdemeester/containerd,kunalkushwaha/containerd,miaoyq/containerd,estesp/containerd,xiekeyang/containerd,rajasec/containerd,miaoyq/containerd,chanezon/containerd