PR30348: debuginfod: retry partial archive scans

PR30348: debuginfod: retry partial archive scans

On some public debuginfod servers, it was observed that errors
may occur during individual archive scanning operations.  That's
fine, but previous code still went ahead and marked the archive
"done" by inserting a record into the *_file_mtime_scanned table.

New code ensures that exceptions propagate for these cases, and an
archive that encountered an error while scanning will be retried
later.

Signed-off-by: Frank Ch. Eigler <fche@redhat.com>