avoid cleaning up move log when drop from remote fails

avoid cleaning up move log when drop from remote fails

move: Improve resuming a move that succeeded in transferring the content,
but where dropping failed due to eg a network problem, in cases where
numcopies checks prevented the resumed move from dropping the object from
the source repository.

This was earlier done for moves that got interrupted during the drop stage.

Sponsored-by: Svenne Krap on Patreon