dkron shell based jobs fail

[michielroding]

Describe the bug
Since upgrading from dkron v4.0.2 v4.0.4, our shell based jobs fail with the message
rpc error: code = Unavailable desc = connection error: desc = "transport: error while dialing: dial unix /tmp/plugin1410549518: connect: connection refused"

To Reproduce
Steps to reproduce the behavior:

1. On ubuntu 20.04, install dkron via apt
2. Use the dkron.yml

server: true
bootstrap-expect: 1
retry-join:
  - some-machine
data-dir: /var/lib/dkron.data
disable-usage-stats: true

3. Start the dkron service
4. Run a shell based job from the UI. Job is considered succesful.
5. Notice that the /usr/bin/dkron shell process is gone from ps aux

Expected behavior
Complete the job

Screenshots

Specifications:

• OS: Ubuntu
• Version: 20.04
• Executor: shell

Additional context