tmf: Update the refresh handler

tmf: Update the refresh handler

- Remove delay when the handler is not busy
- Allow any Object as source to allow a component to queue different
  types of update that don't cancel each other
- Only execute one update at a time to allow other (non-coalesced) UI
  runnables to execute between updates and to allow updates from other
  sources to be replaced while the handler is busy

Change-Id: I9af49d6a11e8e224bc7ff527ba592c238715c7d7
Signed-off-by: Patrick Tasse <patrick.tasse@gmail.com>
Reviewed-on: https://git.eclipse.org/r/30341
Reviewed-by: Bernd Hufmann <bernd.hufmann@ericsson.com>
Tested-by: Hudson CI