Change message in help.

Changed description -d option.

pym/cl_install_cmd.py

@@ -30,7 +30,9 @@ CMD_OPTIONS = [{'shortOption':"d",
                 'longOption':"disk",
                 'optVal':"DISK[:[DIR:FILESYSTEM:OPTIONS]]",
                 'action':'append',
-                'help':_("the DISK for installation, which mounted to DIR")
+                'help':_("the DISK for installation, which mounted to DIR") +
+                    ". " 
+               +_("DIR with value 'none' will cancels the mount point transfer")
                },
                {'shortOption':"b",
                 'longOption':"bind",