chrattr-util: return EOPNOTSUPP from chrattr_full if no other failure was observed

When chattr_full tries to apply flags one-by-one, and one fails,
record which errno was returned. But record EOPNOTSUPP(&friends)
only if no other error is observed, and return it only in that case
(otherwise keep returning ENOANO), so that callers can respond
appropriately to EOPNOTSUPP vs more relevant errors.
For example, this lets tmpfiles.d log at debug level when a filesystem
flag cannot be applied because the filesystem does not support it,
but at warning level if something else went wrong when applying it.
Restores logging behaviour of tmpfiles.d to pre-250.

Follow-up for: https://github.com/systemd/systemd/commit/c1631ee124a30abfb9c71e2a1534b8afffc3b6a7

Fixes: https://github.com/systemd/systemd/issues/21901