Set max_microversion 2.42 for hosts tests

The compute os-hosts API is deprecated as of the 2.43 microversion,
so we should set max_microversion = '2.42' for hosts tests.

ref:
https://developer.openstack.org/api-ref/compute/#list-hosts

Change-Id: Icc320de1fac272c8973edada7a556079b3dbf5a7
2 files changed