allow to mount virtual folders on root (/) path

Fixes #783

Signed-off-by: Nicola Murino <nicola.murino@gmail.com>

vfs/cryptfs.go

@@ -44,7 +44,7 @@ func NewCryptFs(connectionID, rootDir, mountPath string, config CryptFsConfig) (
 			name:         cryptFsName,
 			connectionID: connectionID,
 			rootDir:      rootDir,
-			mountPath:    mountPath,
+			mountPath:    getMountPath(mountPath),
 		},
 		masterKey: []byte(config.Passphrase.GetPayload()),
 	}