Fix runners to do their best to gracefully stop on pod eviction (#1759)

Ref #1535
Ref #1581

Signed-off-by: Yusuke Kuoka <ykuoka@gmail.com>

runner/entrypoint-dind.sh

@@ -0,0 +1,69 @@
+#!/bin/bash
+source logger.sh
+source graceful-stop.sh
+trap graceful_stop TERM
+
+sudo /bin/bash <<SCRIPT
+mkdir -p /etc/docker
+
+if [ ! -f /etc/docker/daemon.json ]; then
+  echo "{}" > /etc/docker/daemon.json
+fi
+
+if [ -n "${MTU}" ]; then
+jq ".\"mtu\" = ${MTU}" /etc/docker/daemon.json > /tmp/.daemon.json && mv /tmp/.daemon.json /etc/docker/daemon.json
+# See https://docs.docker.com/engine/security/rootless/
+echo "environment=DOCKERD_ROOTLESS_ROOTLESSKIT_MTU=${MTU}" >> /etc/supervisor/conf.d/dockerd.conf
+fi
+
+if [ -n "${DOCKER_REGISTRY_MIRROR}" ]; then
+jq ".\"registry-mirrors\"[0] = \"${DOCKER_REGISTRY_MIRROR}\"" /etc/docker/daemon.json > /tmp/.daemon.json && mv /tmp/.daemon.json /etc/docker/daemon.json
+fi
+SCRIPT
+
+dumb-init bash <<'SCRIPT' &
+source logger.sh
+source wait.sh
+
+dump() {
+  local path=${1:?missing required <path> argument}
+  shift
+  printf -- "%s\n---\n" "${*//\{path\}/"$path"}" 1>&2
+  cat "$path" 1>&2
+  printf -- '---\n' 1>&2
+}
+
+for config in /etc/docker/daemon.json /etc/supervisor/conf.d/dockerd.conf; do
+  dump "$config" 'Using {path} with the following content:'
+done
+
+log.debug 'Starting supervisor daemon'
+sudo /usr/bin/supervisord -n >> /dev/null 2>&1 &
+
+log.debug 'Waiting for processes to be running...'
+processes=(dockerd)
+
+for process in "${processes[@]}"; do
+    if ! wait_for_process "$process"; then
+        log.error "$process is not running after max time"
+        dump /var/log/dockerd.err.log 'Dumping {path} to aid investigation'
+        dump /var/log/supervisor/supervisord.log 'Dumping {path} to aid investigation'
+        exit 1
+    else
+        log.debug "$process is running"
+    fi
+done
+
+if [ -n "${MTU}" ]; then
+  sudo ifconfig docker0 mtu "${MTU}" up
+fi
+
+startup.sh
+SCRIPT
+
+RUNNER_INIT_PID=$!
+log.notice "Runner init started with pid $RUNNER_INIT_PID"
+wait $RUNNER_INIT_PID
+log.notice "Runner init exited. Exiting this process with code 0 so that the container and the pod is GC'ed Kubernetes soon."
+
+trap - TERM