Function call issue for parsing sentinel_fallback

[itsfarbod]

Hi,
The _parse_sentinel was a class function and when it get called by

sentinel_hosts = [
            _parse_sentinel(fallback)
            for fallback in kwargs.pop('sentinel_fallback', [])
        ]

It made errors because it doesn't pass cls to it and it can't receive the sentinel.
So I made it static and tested it and its OK now.

[tobias-urdin]

@Mergifyio backport stable/4.6

[mergify]

backport stable/4.6

✅ Backports have been created

• #1407 Function call issue for parsing sentinel_fallback (backport #1405) has been created for branch stable/4.6