devel/upload.in: make it more project generic

Only install ganeti specific files if they exist. This way we can call
ganeti's devel/upload in another sub-projects (eg. nbma) and have it
uploaded to a host as well, without having to create a new script there.

Signed-off-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>