event.py: ignore exceptions from stdout and sterr operations in atexit
    
    When atexit functions run, stdout and stderr operations may fail, e.g.
    when output is piped to less but has been exited by the user.
    This removes error print from output of "bitbake -e sqlite3 | less"
    if user presses "q" before bitbake has finished processing:
    
    [Errno 32] Broken pipeError in atexit._run_exitfuncs:
    Traceback (most recent call last):
      File "/home/builder/src/poky/bitbake/lib/bb/event.py", line 135, in print_ui_queue
        sys.stdout.flush()
    
    Signed-off-by: Mikko Rapeli <mikko.rapeli@bmw.de>
    Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>