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

Ref #1535
Ref #1581

Signed-off-by: Yusuke Kuoka <[email protected]>

runner/actions-runner.dockerfile

@@ -117,7 +117,7 @@ RUN mkdir /opt/hostedtoolcache \
 
 # We place the scripts in `/usr/bin` so that users who extend this image can
 # override them with scripts of the same name placed in `/usr/local/bin`.
-COPY entrypoint.sh logger.bash update-status /usr/bin/
+COPY entrypoint.sh startup.sh logger.sh graceful-stop.sh update-status /usr/bin/
 
 # Copy the docker shim which propagates the docker MTU to underlying networks
 # to replace the docker binary in the PATH.
@@ -136,5 +136,5 @@ RUN echo "PATH=${PATH}" > /etc/environment \
 
 USER runner
 
-ENTRYPOINT ["/usr/local/bin/dumb-init", "--"]
+ENTRYPOINT ["/bin/bash", "-c"]
 CMD ["entrypoint.sh"]