Clarify effects of some commands in the man page

[the-sun-will-rise-tomorrow]

Fixes #617.

RFC on wording, maybe "permanent" is not the best way to describe it, but it would address the confusion I had.

[the-sun-will-rise-tomorrow]

Please add a Signed-off-by to the commits to indicate your acceptance of the Developer Certificate of Origin (basically declaring that we can use your contribution in the obvious ways).

Is it OK if I do this pseudonymously (using my GitHub username)?

[smcv]

Is it OK if I do this pseudonymously (using my GitHub username)?

Hmm. I would personally be fine with that, but it isn't my project or my policy, and https://github.com/containers/common/blob/main/CONTRIBUTING.md does say no anonymous or pseudonymous contributions.

@cgwalters, @alexlarsson, do you intend to be enforcing that policy for this project?