Add new cfssl image and update e2e tests to use it

images/cfssl/rootfs/Dockerfile

@@ -0,0 +1,24 @@
+# Copyright 2019 The Kubernetes Authors. 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.
+
+FROM alpine:3.11
+
+RUN echo "@testing http://nl.alpinelinux.org/alpine/edge/testing" >> /etc/apk/repositories
+RUN apk add --no-cache \
+    bash \
+    cfssl@testing
+
+EXPOSE 8888
+
+CMD ["cfssl"]