Resolves prometheus/node_exporter#585 (#586)

* Resolves prometheus/node_exporter#585

* - removed 'docker rm' as it is not allowed on CircleCI
See discussion: https://discuss.circleci.com/t/docker-error-removing-intermediate-container/70

test_image.sh

@@ -4,20 +4,27 @@ set -exo pipefail
 docker_image=$1
 port=$2
 
+container_id=''
+
 wait_start() {
     for in in {1..10}; do
-    if  /usr/bin/curl -s -m 5 -f "http://localhost:${port}/metrics" > /dev/null ; then exit 0 ;
+        if  /usr/bin/curl -s -m 5 -f "http://localhost:${port}/metrics" > /dev/null; then
+            docker_cleanup
+            exit 0
         else
             sleep 1
         fi
     done
 
     exit 1
-
 }
 
 docker_start() {
-    docker run -d -p "${port}":"${port}" "${docker_image}"
+    container_id=$(docker run -d -p "${port}":"${port}" "${docker_image}")
+}
+
+docker_cleanup() {
+    docker kill "${container_id}"
 }
 
 if [[ "$#" -ne 2 ]] ; then