Fix mass-deletion of sessions on the settings -> API page

[DL6ER]

What does this implement/fix?

See title and related Discourse topic.

Related issue or feature (if applicable): N/A

Pull request in docs with documentation (if applicable): N/A

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[PromoFaux]

Something not quite right here. Sometimes it deletes all but one session. Seems a bit random as to which session gets left over.

[yubiuser]

Maybe it's an issue with ownSessionID

[rdwebdesign]

I wasn't able to replicate the "all but one" issue using different browsers (Chrome, Firefox and Edge) on the same machine.

You used different windows from the same browser (using incognito mode). I'm not sure if this could be related to the issue you are seeing. We probably need more tests.

[DL6ER]

The issue was the concurrency of the deletions. This is fixed by the latest commit

[yubiuser]

We have 3 functions now with very similar names: deleteSessions(), delSessions(ids) and delSession(id,...). The first one does not do much on it's own, maybe the single line var ids = [$(this).attr("data-del-id")]; can be part of delSessions()?