defer write permissions checking in import until after copy to repo

This should complete the fix started in
6329997ac4, fixing the actual cause of the
test suite failure this time.

Sponsored-by: Dartmouth College's Datalad project

Command/Add.hs

@@ -188,6 +188,7 @@ perform o file addunlockedmatcher = withOtherTmp $ \tmpdir -> do
 	let cfg = LockDownConfig
 		{ lockingFile = lockingfile
 		, hardlinkFileTmpDir = Just tmpdir
+		, checkWritePerms = True
 		}
 	ld <- lockDown cfg (fromRawFilePath file)
 	let sizer = keySource <$> ld