Replace list_hypervisors with list_services

This fixes a regression introduced with commit 88c7ea8 which replaced
list_hosts with list_hypervisors because the former is deprecated.
However, the hypervisor_hostname cannot be used as replacement for
compute hostname. This patch fixes the problem by switching to
list_services which returns compute hostnames.

Change-Id: I948429075e71e11e091703c4b12378c71c37bc29
2 files changed