Add info_cache as expected attribute when evacuate instance

Nova evacuates instance failed with neutron. The reason is
when nova-conductor try to get network info for instance, it
need instance include 'info_cache', but the instance dict which
passed didn't include it. This patch adds 'info_cache' as the
expected attribute for get instance.

Change-Id: I6f110c607e32b0ab536916741605b25d572331dc
Closes-Bug: #1284709
Merge "Add info_cache as expected attribute when evacuate instance"