ssh into default vagrant host without running "vagrant ssh" by passing the configuration parameters vagrant uses for ssh
ssh vagrant@127.0.0.1 -p 2222 -o Compression=yes -o DSAAuthentication=yes -o LogLevel=FATAL -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o IdentitiesOnly=yes -i ~/.vagrant.d/less_insecure_private_key -o ForwardAgent=yes