packaging: setup: use ssh public key for allinone

Instead of asking for the local root password, add the engine's
public key to ~root/.ssh/authorized_keys and change the sdk call
to use public key authentication.

Change-Id: I885894bba4c998e5dd3e9b2fd4da61d833f7a3a1
Signed-off-by: Yedidyah Bar David <didi@redhat.com>