rpc: add 0x prefix to the getbestblockhash answer

For consistency with C# nodes that do add it to their answers.

pkg/rpc/server.go

@@ -117,7 +117,7 @@ Methods:
 	switch req.Method {
 	case "getbestblockhash":
 		getbestblockhashCalled.Inc()
-		results = s.chain.CurrentBlockHash().ReverseString()
+		results = "0x" + s.chain.CurrentBlockHash().ReverseString()
 
 	case "getblock":
 		getbestblockCalled.Inc()

pkg/rpc/server_test.go

@@ -28,7 +28,7 @@ func TestRPC(t *testing.T) {
 		var res StringResultResponse
 		err := json.Unmarshal(bytes.TrimSpace(body), &res)
 		assert.NoErrorf(t, err, "could not parse response: %s", body)
-		assert.Equal(t, chain.CurrentBlockHash().ReverseString(), res.Result)
+		assert.Equal(t, "0x"+chain.CurrentBlockHash().ReverseString(), res.Result)
 	})
 
 	t.Run("getblock", func(t *testing.T) {