enable forwardRetry for command-line transfers

If a transfer fails for some reason, but some data managed to be sent, the
transfer will be retried. (The assistant already did this.)

Possible impacts:

* More ssh prompts if ssh needs to prompt for a password to connect to a
  host, or is prompting about some other problem like a ssh key mismatch.

* More data transfer due to retrying, epecially when a remote does not
  support resuming a transfer.

  In the worst case, a lot of data will be transferred but it fails before
  the end, and then all that data gets transferred again plus one byte more;
  repeat until it manages to get the whole file.

Command/Get.hs

@@ -109,7 +109,7 @@ getKey' key afile = dispatch
 			either (const False) id <$> Remote.hasKey r key
 		| otherwise = return True
 	docopy r witness = getViaTmp (RemoteVerify r) key $ \dest ->
-		download (Remote.uuid r) key afile noRetry
+		download (Remote.uuid r) key afile forwardRetry
 			(\p -> do
 				showAction $ "from " ++ Remote.name r
 				Remote.retrieveKeyFile r key afile dest p