Enable upload of more than 1000 files

reproduced in the environment: http://preview.default-pr-54-nuxeo-aspera-connector.jenkins.l2it.35.231.200.170.nip.io/nuxeo/ui/#!/aspera see the proper preview link below in the comments.

How to reproduce

• go to nuxeo upload with aspera
• create a new upload with 2000 files
• The aspera systray window starts the upload; however the final file upload is never "finished", and status never switches to "done"

expected : the transfer can be completed normally