webui: Don't act on keyboard events which originated in different dialog
    
    Fixes issue when:
    1. 2 dialogs are opened
    2. top dialog's close button is focused
    3. user presses enter to execute 'close' action
    4. dialog is immediately closed (enter key is still pressed)
    5. second dialog automatically receives focus (it's top dialog now)
    6. user releases the key
    7. second dialog reacts to keyup event - which is by default confirmation mixin's confirm event
    8. UNDESIRED behavior occurs
    
    Now confirmation mixin remembers which keys were pressed and released and reacts only to those which originated there.
    
    https://fedorahosted.org/freeipa/ticket/4098
    
    Reviewed-By: Adam Misnyovszki <amisnyov@redhat.com>