Re-enable accumulating transfer failure log files for command-line actions

This was disabled in commit 61ccf95004,
because only the assistant used them, and they were clutter. But, now
--failed also uses them.

Remove the failure log files after successful transfers. Should avoid
most of the clutter problems.

Commit 61ccf95004 mentions a subtle behavior
change, which has now been reverted:

    There is one behavior change from this. If glacier is being used, and a
    manual git annex get --from glacier fails because the file isn't available
    yet, the assistant will no longer later see that failed transfer file and
    retry the get.

Command/TransferKeys.hs

@@ -35,13 +35,13 @@ start = do
   where
 	runner (TransferRequest direction remote key file)
 		| direction == Upload = notifyTransfer direction file $
-			upload (Remote.uuid remote) key file forwardRetry observer $ \p -> do
+			upload (Remote.uuid remote) key file forwardRetry noObserver $ \p -> do
 				ok <- Remote.storeKey remote key file p
 				when ok $
 					Remote.logStatus remote key InfoPresent
 				return ok
 		| otherwise = notifyTransfer direction file $
-			download (Remote.uuid remote) key file forwardRetry observer $ \p ->
+			download (Remote.uuid remote) key file forwardRetry noObserver $ \p ->
 				getViaTmp (RemoteVerify remote) key $ \t -> do
 					r <- Remote.retrieveKeyFile remote key file t p
 					-- Make sure we get the current
@@ -49,9 +49,6 @@ start = do
 					-- not old cached data.
 					Database.Keys.closeDb			
 					return r
-	
-	observer False t tinfo = recordFailedTransfer t tinfo
-	observer True _ _ = noop
 
 runRequests
 	:: Handle