ssh connections to guest time out

[Matthew Treinish]

During the tempest scenario test: test_network_basic_ops the step where the test tries to login into the guest fails with a ssh timeout.

With this traceback:
Traceback (most recent call last):
  File "tempest/scenario/test_network_basic_ops.py", line 269, in test_network_basic_ops
    self._check_public_network_connectivity()
  File "tempest/scenario/test_network_basic_ops.py", line 258, in _check_public_network_connectivity
    raise exc
SSHTimeout: Connection to the 172.24.4.232 via SSH timed out.
User: cirros, Password: None

Logs for the failed run are here:

http://logs.openstack.org/88/52988/9/gate/gate-tempest-devstack-vm-neutron-pg-isolated/2bf5a98/