Ensure only a single running instance of Sinter

[mike-myers-tob]

Why

As a security engineer, I want to be ensured that only one Sinter instance is running at any given time to reduce conflicts and potential machine locking.

Acceptance Criteria

• Ensure that no more than one instance of Sinter is running at any time.

Dev Notes

One suggested approach is the creation of a 'pid file' in a root-owned path like /private/var/tmp