Convert result of hosts.values() to list always

In Python 3 dict.values() returns a dictionary view object
which don't support indexing.
Because of that some tests in
tempest.api.compute.admin.test_servers_on_multinodes module
were failing when running on python 3.

This patch fixes this issue by converting result of dict.values()
method to list always.

Change-Id: I5580dd7a6f22fbe880ea81b3e36b3d6111209958
1 file changed