[Bug Fix] Prevent Double Shutdown Issues

[koolzz]

Before if onvm_nflib_stop would be called 2 times we would see weird behavior, this PR fixes that by adding an atomic flag such that we only execute the shutdown sequence once.

Kudos to @dennisafa for finding this

This PR includes
Resolves issues
Breaking API changes
Internal API changes
Usability improvements
Bug fixes
New functionality
New NF/onvm_mgr args
Changes to starting NFs
Dependency updates
Web stats updates

Merging notes:

• Dependencies: None

TODO before merging :

• [ ] PR is ready for review

Test Plan:

Review:

@dennisafa pls

[onvm]

In response to PR creation

CI Message

Your results will arrive shortly