Dynamically set test image name

test/docker/Gopkg.toml

@@ -0,0 +1,20 @@
+# © Copyright IBM Corporation 2017
+#
+# 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.
+
+[[constraint]]
+  name = "github.com/docker/docker"
+  version = "^1.12"
+
+[[constraint]]
+  name = "github.com/docker/go-connections"