Tmp refs files are not deleted when no longer required

[doulikecookiedough]

During the process to create refs files via tag_object, unnecessary cid* refs files are not being removed and building up in the /tmp directory.

Investigate the cause and resolve.

[doulikecookiedough]

This has been resolved via BugFix-101: cid refs file does not get cleaned up

Note:

• The atexit module should have handled clean up of cid refs files that were not moved/renamed, however it does not appear to have executed. I was unable to identify the exact cause, but creating files ahead of time is inefficient (not a good design choice). So tag_object has been revised to only create files when it is required, and this change appears to have resolved this issue.
• While it's not clear why atexit functions did not execute after the python interpreter exited, I don't believe this to be a major issue. I am moving forward with this fix with the caveat that there is some unexpected behaviour with atexit that may need to be further investigated when time-permitting.