ClearCase Plugin performs a "reserved" checkout even if the checkbox "reserved" is not checked

When checkin out a file, the user has the option to check out "unreserved" by unchecking the "reserved" checkbox in the checkout dialog.

Unfortunately, the ClearCase plugin does only neglect the "-reserved" option when sending the command. But the "-unreserved" option has to be set, if the checkout has to be unreserved.