stream through proxy when using fileRetriever

The problem was that when the proxy requests a key be retrieved to its
own temp file, fileRetriever was retriving it to the key's temp
location, and then moving it at the end, which broke streaming.

So, plumb through the path where the key is being retrieved to.

Remote/Helper/Chunked.hs

@@ -294,8 +294,10 @@ retrieveChunks retriever u vc chunkconfig encryptor basek dest basep enc encc
 			let p = maybe basep
 				(offsetMeterUpdate basep . toBytesProcessed)
 				offset
-			v <- tryNonAsync $
-				retriever (encryptor k) p Nothing $ \content ->
+			v <- tryNonAsync $ do
+				let enck = encryptor k
+				objloc <- fromRepo $ gitAnnexTmpObjectLocation enck
+				retriever enck p objloc Nothing $ \content ->
 					bracket (maybe opennew openresume offset) (liftIO . hClose . fst) $ \(h, iv) -> do
 						retrieved iv (Just h) p content
 						let sz = toBytesProcessed $
@@ -316,7 +318,9 @@ retrieveChunks retriever u vc chunkconfig encryptor basek dest basep enc encc
 	getrest p h iv sz bytesprocessed (k:ks) = do
 		let p' = offsetMeterUpdate p bytesprocessed
 		liftIO $ p' zeroBytesProcessed
-		retriever (encryptor k) p' Nothing $ 
+		let enck = encryptor k
+		objloc <- fromRepo $ gitAnnexTmpObjectLocation enck
+		retriever enck p' objloc Nothing $ 
 			retrieved iv (Just h) p'
 		getrest p h iv sz (addBytesProcessed bytesprocessed sz) ks
 
@@ -324,7 +328,7 @@ retrieveChunks retriever u vc chunkconfig encryptor basek dest basep enc encc
 		iv <- startVerifyKeyContentIncrementally vc basek
 		case enc of
 			Just _ -> do
-				retriever (encryptor basek) basep Nothing $
+				retriever (encryptor basek) basep (toRawFilePath dest) Nothing $
 					retrieved iv Nothing basep
 				return (Right iv)
 			-- Not chunked and not encrypted, so ask the
@@ -333,7 +337,7 @@ retrieveChunks retriever u vc chunkconfig encryptor basek dest basep enc encc
 			-- passing the whole file content to the
 			-- incremental verifier though.
 			Nothing -> do
-				retriever (encryptor basek) basep iv $
+				retriever (encryptor basek) basep (toRawFilePath dest) iv $
 					retrieved iv Nothing basep
 				return $ case iv of
 					Nothing -> Right iv