Rewrite PID files automatically for multiple parallel Omnibus backup/restore

Summary

As part of !97218 (merged), we created a PID lock mechanism to detect if there is another backup and restore process in progress. As a follow-up, we should improve the user experience by validating if the PID exists in the system against the PID file that was not removed due to unexpected termination signals while running the rake task.

Proposal

• Validate the existence of the PID process in the system.
• If there is no PID found, then proceed to rewrite the PID file: /tmp/backup_restore.pid

More context: !97218 (comment 1104008300)