Add gate_hook and post_test_hook

We are setting up a devstack job for this plugin. These hooks will
be leveraged by the job.

Change-Id: I751c46bcc1768894f588c0f6689555a4392082b0

contrib/gate_hook.sh

@@ -0,0 +1,21 @@
+#!/bin/bash -x
+#
+# 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.
+#
+# This script is executed inside gate_hook function in devstack gate.
+
+
+# Keep all devstack settings here instead of project-config for easy
+# maintain if we want to change devstack config settings in future.
+
+$BASE/new/devstack-gate/devstack-vm-gate.sh

contrib/post_test_hook.sh

@@ -0,0 +1,44 @@
+#!/bin/bash -x
+#
+# 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.
+
+# This script is executed inside post_test_hook function in devstack gate.
+
+# Sleep some time until all services are starting
+sleep 5
+
+# Check if a function already exists
+function function_exists {
+    declare -f -F $1 > /dev/null
+}
+
+if ! function_exists echo_summary; then
+    function echo_summary {
+        echo $@
+    }
+fi
+
+# Save trace setting
+XTRACE=$(set +o | grep xtrace)
+set -o xtrace
+
+echo_summary "Devstack-plugin-container's post_test_hook.sh was called..."
+(set -o posix; set)
+
+# Verify that Docker is installed correctly by running the hello-world image
+sudo -H -u stack docker run hello-world
+
+EXIT_CODE=$?
+
+$XTRACE
+exit $EXIT_CODE

devstack/lib/docker

@@ -48,6 +48,7 @@ function install_docker {
     local arch=$(dpkg --print-architecture)
     if is_ubuntu; then
         apt_get install linux-image-extra-$(uname -r) linux-image-extra-virtual
+        apt_get install apt-transport-https ca-certificates software-properties-common
         curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
         sudo add-apt-repository -y \
             "deb [arch=${arch}] https://download.docker.com/linux/${lsb_dist} \