Compose test-with-docker with start-docker to reduce duplication

- inline the contents of `checkdocker.sh`

scripts/start-docker

@@ -4,9 +4,11 @@ set -euo pipefail
 RELEASE_PATH="$(cd "$(dirname "$0")/.." && pwd)"
 export RELEASE_PATH
 
-. "${RELEASE_PATH}/scripts/checkdocker.sh"
-
-if user_can_docker; then
+# The Docker CLI does not need to be run as root in order to be safe in all
+# cases. For example, when running on MacOS it is quarantined to a different
+# virtual machine. If you are running daemon on a local machine then practice
+# caution with sudo-less docker invocations.
+if ! docker info 2>&1 | grep -q "permission denied"; then
   DOCKER="docker"
 else
   # On development workstations docker must run as root.
@@ -19,4 +21,4 @@ $DOCKER run \
   --privileged \
   -v  "${RELEASE_PATH}:/bpm" \
   -it cfbpm/bpm-ci:latest \
-  /bin/bash
+  "${@:-/bin/bash}"

scripts/test-with-docker

@@ -4,20 +4,4 @@ set -euo pipefail
 RELEASE_PATH="$(cd "$(dirname "$0")/.." && pwd)"
 export RELEASE_PATH
 
-. "${RELEASE_PATH}/scripts/checkdocker.sh"
-
-if user_can_docker; then
-  DOCKER="docker"
-else
-  # On development workstations docker must run as root.
-  # These settings are not related to the privileges that bpm creates runc containers with.
-  DOCKER="sudo docker"
-fi
-
-$DOCKER pull cfbpm/bpm-ci:latest
-
-$DOCKER run \
-  --privileged \
-  -v "${RELEASE_PATH}:/bpm" \
-  -t cfbpm/bpm-ci:latest \
-  /bpm/scripts/test-unit "$@"
+"${RELEASE_PATH}/scripts/start-docker" /bpm/scripts/test-unit