The service_mapped_to_host filter is used to check if a service is
mapped to a host, based on the group for the service or its
host_in_groups attribute if one exists. We check if the service's group
is in the 'groups' list. However, to get the list of groups to which a
host belongs, we should use the 'group_names' list.
This filter is currently only used in neutron IPv6 module loading, so
the effects are minimal.
Change-Id: I37409ca8d273b0426df0a648db222dc5432e738a
Closes-Bug: #1868285
35966c9186