Fix package verify script no longer working under CentOS 6.

/sbin/init has gone missing in newer version of the centos:6 image, so
we need to manually install it first.

Author: GUI

build/package/verify/docker_run

@@ -6,15 +6,37 @@ source_dir="$(dirname "$(dirname "$(dirname "$(cd "$(dirname "${BASH_SOURCE[0]}"
 docker_image=${DIST/-/:}
 container_name="api-umbrella-package-$DIST-verify"
 container_name=${container_name//[^a-zA-Z0-9_.-]/}
+init_container_name="${container_name}-init"
 
 # Wipe any previous build attempts.
+existing=$(docker ps -a -q --filter="name=$init_container_name")
+if [ "$existing" != "" ]; then
+  docker rm -f "$existing"
+fi
 existing=$(docker ps -a -q --filter="name=$container_name")
 if [ "$existing" != "" ]; then
   docker rm -f "$existing"
 fi
+existing=$(docker images -a -q --filter="reference=$init_container_name")
+if [ "$existing" != "" ]; then
+  docker rmi -f "$existing"
+fi
 
-# Run inside a privileged container for systemd things to work. First run
+install_init_cmd=""
+if [ "$DIST" == "centos-6" ]; then
+  # CentOS 6 docker image no longer has /sbin/init pre-installed:
+  # https://github.com/CentOS/sig-cloud-instance-images/issues/28#issuecomment-306801650
+  install_init_cmd="yum -y install initscripts"
+fi
+
+# Run inside a privileged container for systemd things to work. First install
+# /sbin/init (it's missing from some docker base images), and then run
 # /sbin/init so we can better emulate a real server for systemd testing.
+docker run \
+  --name="$init_container_name" \
+  "$docker_image" \
+  bash -c "$install_init_cmd"
+docker commit "$init_container_name" "$init_container_name"
 docker run \
   --name="$container_name" \
   --volume="$source_dir:/api-umbrella" \
@@ -23,7 +45,7 @@ docker run \
   --tty \
   --privileged \
   --detach \
-  "$docker_image" \
+  "$init_container_name" \
   /sbin/init
 
 # Next run our script to install the API Umbrella package and perform
@@ -32,6 +54,8 @@ docker exec --tty "$container_name" /bin/bash -c "/api-umbrella/build/package/ve
 
 # Delete after successful run.
 docker stop "$container_name"
+docker rm -f "$init_container_name"
 docker rm -f "$container_name"
+docker rmi -f "$init_container_name"
 
 echo "Completed package verification for $DIST"