Fix warnings reported by Go 1.6 "go tool vet -shadow=true"

Warnings were:

  main.go:234: declaration of err shadows declaration at main.go:163:
  internal/fusefrontend/file.go:401: declaration of err shadows declaration at internal/fusefrontend/file.go:379:
  internal/fusefrontend/file.go:419: declaration of err shadows declaration at internal/fusefrontend/file.go:379:
  internal/fusefrontend/fs_dir.go:140: declaration of err shadows declaration at internal/fusefrontend/fs_dir.go:97:

1 files changed, 1 insertions, 1 deletions

diff --git a/main.go b/main.go
index 404b1ef..6896f11 100644
--- a/main.go
+++ b/main.go
@@ -231,7 +231,7 @@ func main() {
 	// Every operation below requires CIPHERDIR. Check that we have it.
 	if flagSet.NArg() >= 1 {
 		args.cipherdir, _ = filepath.Abs(flagSet.Arg(0))
-		err := checkDir(args.cipherdir)
+		err = checkDir(args.cipherdir)
 		if err != nil {
 			toggledlog.Fatal.Printf(colorRed+"Invalid cipherdir: %v\n"+colorReset, err)
 			os.Exit(ERREXIT_CIPHERDIR)