print an error message if neo4j is already running

[xavieryao]

Bug: neo4j container sometimes fails to start without outputting any message, after being forced to stop.

This happens if the --time / stop_grace_period of docker stop or docker compose stop is not long enough, for example the default value 10 seconds. The output of https://github.com/neo4j/docker-neo4j/blob/0c091859a7d1d487452b7fd7abe70599d48fed4d/docker-image-src/4.4/docker-entrypoint.sh#L560

will become Neo4j is already running (pid:1), but the entry point script will not show any error message.

It will be really helpful for users to debug if the entry point script could point out why neo4j console --dry-run fails, or at least print an error message if the problem is that the pid file already exists and provide some solutions (what I did in this PR).

• Steps to reproduce.

docker create --name neo4j neo4j:4.4-community
docker start neo4j
# wait after neo4j is started
docker stop neo4j -t 10 # default is 10 seconds, lower the value if not able to reproduce
docker start -ai neo4j

• Expected behaviour: neo4j starts, or shows a message about why it fails to start
• Actual behaviour: containers exits with code 1, without any output.
• Neo4j image tag being used: neo4j:4.4-community. I assume this also applies to other tags.
• The output of the docker version command

Server: Docker Engine - Community
 Engine:
  Version:          20.10.16
  API version:      1.41 (minimum version 1.12)
  Go version:       go1.17.10
  Git commit:       f756502
  Built:            Thu May 12 09:15:28 2022
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.6.4
  GitCommit:        212e8b6fa2f44b9c21b2798135fc6fb7c53efc16
 runc:
  Version:          1.1.1
  GitCommit:        v1.1.1-0-g52de29d
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0