use environment AUTO_FLY to control if autofly

Change-Id: Ie47dfdc5f3b07f6e1a6336fc235ac6ccd5d53cab
Reviewed-on: https://gerrit.libreoffice.org/11540
Reviewed-by: Kohei Yoshida <libreoffice@kohei.us>
Tested-by: Kohei Yoshida <libreoffice@kohei.us>