When uploading docs, use rsync -p to set permissions

When uploading docs, use rsync -p to set permissions

It turns out that rsync --chmod means "pretend the source files had
already had this chmod operation applied to them", and not "chmod the
destination files" like you'd expect.

As a result, the -p (--perms) option is also needed, so that rsync will
"preserve" the modified permissions. Otherwise, the docs will not be
group-writeable as intended, and only the person who made the previous
upload will be able to upload them next time.

Bug: https://bugs.freedesktop.org/show_bug.cgi?id=36130
Reviewed-by: Will Thompson <will.thompson@collabora.co.uk>