Avoid log error message when not using Archiver

[qqmyers]

if :ArchiverClassName is not set (the default case), things work, but the null classname results in a log message noting that an archiver class can't be loaded. There's no need for such a message - it just pollutes the log. I'll send a PR to suppress it.

[qqmyers]

Actually, this should only happen if an archiver workflow is set up, or if you call the submitToArchive api call, or with the new 'update current version' code in #5541, so it should not be affecting v4.11 users who haven't ever set up archiving (just @kcondon during his testing... sorry).

[qqmyers]

fixing in #5541...

[pdurbin]

I just moved this to QA since it's part of the pull request currently under test.