Fix #97 - progress events might arrive _after_ the success callback
Fix #97 - progress events might arrive _after_ the success callback

Don't accidentally recreate the progress bar if we are unlucky (bug
only visible in Firefox)

dronekit/droneshare,diydrones/droneshare,diydrones/droneshare,PHELiOX/droneshare,SecureCloud-biz/droneshare,dronekit/droneshare,SecureCloud-biz/droneshare,PHELiOX/droneshare,PHELiOX/droneshare,diydrones/droneshare,SecureCloud-biz/droneshare,dronekit/droneshare