admit: Fix tempfile security (fixes #4)
admit: Fix tempfile security (fixes #4)

ssh-keygen makes up its own filename without taking special
precautions about being in a shared tmp directory, so do it in our own
temporary directory instead.

Signed-off-by: Anders Kaseorg <087231934ba8fcf78bc142ce37d193b895ac03c4@mit.edu>

sipb/homeworld,sipb/homeworld,sipb/homeworld,sipb/homeworld