fix: shellcheck warnings in docker run.sh

[ilyam8]

Summary

This PR fixes shellcheck warnings (SC2012) in our docker run.sh file. Thanks to @maneamarius for noticing the problem and suggesting the solution.

Test Plan

Compare the output using the old and new code

$ ls -nd /var/run/docker.sock | awk '{print $4}'
997
$ stat -c %g /var/run/docker.sock 2>/dev/null
997

Additional Information

[Ferroin]

@ilyam8 See #12378 for a fix for the CI failure.

[ilyam8]

@Ferroin the problem was exiting after unsuccessful stat. I didn't notice we have set -e 😅