VOL-1460 Updated core to use voltha-protos instead of local protos
Moved protos to python directory in order to maintain functionaly of containers built there.
Added capability to do local builds of protos
Added instructions on running dep ensure for getting protos.
Updated github.com/golang/protobuf version to v1.3.1

Change-Id: Ia6ef55f07f0d5dcb5b750d7c37b21b71db85bfc4
diff --git a/vendor/go.etcd.io/etcd/clientv3/op.go b/vendor/go.etcd.io/etcd/clientv3/op.go
index 13507c9..085dd28 100644
--- a/vendor/go.etcd.io/etcd/clientv3/op.go
+++ b/vendor/go.etcd.io/etcd/clientv3/op.go
@@ -218,6 +218,10 @@
 
 // OpGet returns "get" operation based on given key and operation options.
 func OpGet(key string, opts ...OpOption) Op {
+	// WithPrefix and WithFromKey are not supported together
+	if isWithPrefix(opts) && isWithFromKey(opts) {
+		panic("`WithPrefix` and `WithFromKey` cannot be set at the same time, choose one")
+	}
 	ret := Op{t: tRange, key: []byte(key)}
 	ret.applyOpts(opts)
 	return ret
@@ -225,6 +229,10 @@
 
 // OpDelete returns "delete" operation based on given key and operation options.
 func OpDelete(key string, opts ...OpOption) Op {
+	// WithPrefix and WithFromKey are not supported together
+	if isWithPrefix(opts) && isWithFromKey(opts) {
+		panic("`WithPrefix` and `WithFromKey` cannot be set at the same time, choose one")
+	}
 	ret := Op{t: tDeleteRange, key: []byte(key)}
 	ret.applyOpts(opts)
 	switch {
@@ -544,3 +552,9 @@
 	ret.applyOpts(opts)
 	return &pb.LeaseTimeToLiveRequest{ID: int64(id), Keys: ret.attachedKeys}
 }
+
+// isWithPrefix returns true if WithPrefix is being called in the op
+func isWithPrefix(opts []OpOption) bool { return isOpFuncCalled("WithPrefix", opts) }
+
+// isWithFromKey returns true if WithFromKey is being called in the op
+func isWithFromKey(opts []OpOption) bool { return isOpFuncCalled("WithFromKey", opts) }