webadmin: fix duplicate events search results on Enter

This is a workaround for GWT bug 3533, "SuggestBox
allows keyUp events to fire twice." The workaround is to
attach the event handler to the SuggestBox's wrapped
TextBox, not to the SuggestBox itself.

Change-Id: I6fa8a023bdecf3d7a23eb10c940e069e2448d2fa
Bug-Url: https://bugzilla.redhat.com/971695
Signed-off-by: Greg Sheremeta <gshereme@redhat.com>