Don't clear real mods in action modmask

Don't clear real mods in action modmask

Previously, we would clear out the real modmask when updating the
modmask for action maps, if not using the key's modmask.  The correct
behaviour here is instead to use the key's modmask if using the modmap,
else use the real mods provided with the action originally.

Signed-off-by: Daniel Stone <daniel@fooishbar.org>