synchronously delete archives
synchronously delete archives

it's safe to delete upgraded metrics asynchronously because they are
removed from indexer and not accessible afterwards. this is not the
case for archives as they may relate to active metrics. we should
delete them completely so we don't access them again.

Change-Id: I3b8baaf1609a003c7d09b59a84570c66035a8183

gnocchixyz/gnocchi,leandroreox/gnocchi,gnocchixyz/gnocchi,leandroreox/gnocchi,sileht/gnocchi,sileht/gnocchi