gstwldisplay: don't break main loop when poll wait was interrupted
requested to merge JaredHu/gstreamer:dont-break-wayland-display-mainloop-when-suspend-resume into main
sometimes when do system suspend resume test, poll wait will return with errno == EINTR, which means poll wait was interrupted by system suspend, need continue main loop instead of break the loop and report communicating error with wayland server because we can resume connection after system resume back.