Bump cfssl to be compatible with Go 1.10

vendor/github.com/google/certificate-transparency-go/client/configpb/gen.go

@@ -0,0 +1,17 @@
+// Copyright 2017 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package configpb
+
+//go:generate protoc -I=. -I=$GOPATH/src --go_out=:. multilog.proto