Rename method get_hosts in admin/info/tables.py

There are 2 identical methods defined in admin/info/tables.py,
Rename get_hosts to get_zone_hosts and get_aggregate_hosts.

Change-Id: Ib3d115737400515c4b31178721609055a9658085
Closes-bug: #1262944
Merge "Rename method get_hosts in admin/info/tables.py"