install docker key before trying to fetch packages

Change-Id: Ie5083cf7bfa2599664e78443a43eda7db86be44a
diff --git a/packer/provision/basebuild.sh b/packer/provision/basebuild.sh
index da4c98f..6acd426 100644
--- a/packer/provision/basebuild.sh
+++ b/packer/provision/basebuild.sh
@@ -6,8 +6,6 @@
 # force any errors to cause the script and job to end in failure
 set -xeu -o pipefail
 
-DOCKER_VERSION=17.09.0
-
 rh_systems() {
     echo 'No changes to apply'
 }
@@ -25,10 +23,14 @@
 ubuntu_systems() {
     apt-get clean
     ubuntu_install_java_setup
+
+    # set up docker repo
+    curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
     sudo add-apt-repository \
         "deb [arch=amd64] https://download.docker.com/linux/ubuntu \
          $(lsb_release -cs) \
          stable"
+    
     apt-get update
     apt-get install -y \
         bzip2 \
@@ -45,7 +47,7 @@
         nodejs-legacy \
         npm \
         python-pip \
-        docker-ce=${DOCKER_VERSION}-ce \
+        docker-ce \
         # end of apt-get install list
     npm install -g bower
     npm install karma --save-dev