metadata: merge snapshot labels with metadata's labels
metadata: merge snapshot labels with metadata's labels

fix the no-op issue.

Signed-off-by: Wei Fu <df4176d36abdc6fd0d966de5d5471522668de494@gmail.com>

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