cmd/containerd: remove cli.Context dependence for content.Store
cmd/containerd: remove cli.Context dependence for content.Store

We've moved to using the config, directly. This removes the argument and
gets rid of a few extra lines of code.

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

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