don't rely on hasKeyCheap in the transfer scan

The problem with using it here is that, if a removable drive is scanned
and gets disconnected during the scan, testing for all the files will
indicate it doesn't have them, and the scan is logged as completed
successfully, without necessary transfers being queued.

Assistant/Threads/TransferScanner.hs

@@ -39,8 +39,6 @@ transferScannerThread st dstatus scanremotes transferqueue = do
 				void $ alertWhile dstatus (scanAlert r) $
 					expensiveScan st dstatus transferqueue r
 				liftIO $ debug thisThread ["finished scan of", show r]
-				runThreadState st $ inRepo $
-					transferScanned $ Remote.uuid r
 			else failedTransferScan st dstatus transferqueue r
 
 {- This is a cheap scan for failed transfers involving a remote. -}
@@ -66,6 +64,8 @@ expensiveScan st dstatus transferqueue r = do
 	g <- runThreadState st $ fromRepo id
 	files <- LsFiles.inRepo [] g
 	go files
+	runThreadState st $ inRepo $
+		transferScanned $ Remote.uuid r
 	return True
 	where
 		go [] = noop
@@ -90,12 +90,6 @@ expensiveScan st dstatus transferqueue r = do
 		u = Remote.uuid r
 		enqueue f t = queueTransferWhenSmall transferqueue dstatus (Just f) t r
 
-		{- Look directly in remote for the key when it's cheap;
+		remotehas key = elem
-		 - otherwise rely on the location log. -}
-		remotehas key
-			| Remote.hasKeyCheap r = (==)
-				<$> pure (Right True)
-				<*> Remote.hasKey r key
-			| otherwise = elem
 			<$> pure u
 			<*> loggedLocations key