server/process: Remove daemonic thread usage
    
    We're seeing UI deadlocks occasionally and this is possibly due to the
    use of a daemonic thread in the UI event queue processing. This thread
    could terminate holding a threading Lock() which would cause issues
    for the process when exitting.
    
    Change the shutdown process to handle this more cleanly.
    
    Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>