Populate NodeAffinity on top of labels for cloud based PersistentVolumes

Signed-off-by: Deep Debroy <ddebroy@docker.com>

pkg/apis/core/v1/helper/helpers.go

@@ -283,6 +283,20 @@ func NodeSelectorRequirementsAsFieldSelector(nsm []v1.NodeSelectorRequirement) (
 	return fields.AndSelectors(selectors...), nil
 }
 
+// NodeSelectorRequirementKeysExistInNodeSelectorTerms checks if a NodeSelectorTerm with key is already specified in terms
+func NodeSelectorRequirementKeysExistInNodeSelectorTerms(reqs []v1.NodeSelectorRequirement, terms []v1.NodeSelectorTerm) bool {
+	for _, req := range reqs {
+		for _, term := range terms {
+			for _, r := range term.MatchExpressions {
+				if r.Key == req.Key {
+					return true
+				}
+			}
+		}
+	}
+	return false
+}
+
 // MatchNodeSelectorTerms checks whether the node labels and fields match node selector terms in ORed;
 // nil or empty term matches no objects.
 func MatchNodeSelectorTerms(