tmf: Fix mouse detect handling in TimeGraphControl

tmf: Fix mouse detect handling in TimeGraphControl

Prevent the menu be shown before mouse up event is received. Otherwise
the zoom won't work. This is because the mouse up event will be received
by the menu pop-up and not by the TimeGraphControl instance.

Change-Id: Iaa905d39205a4a45abb8fd5cfeaac81664561820
Signed-off-by: Bernd Hufmann <Bernd.Hufmann@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/70138
Reviewed-by: Hudson CI
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Tested-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Reviewed-by: Bernd Hufmann <bernd.hufmann@ericsson.com>