Add compute microversions configuration on tempest
Add compute microversions configuration on tempest

Many projects like Nova, Ironic etc have implemented the
microversions for versioning their APIs.

Tempest is going to tests those microversions -
I57b78b4c0543b6fb0533b556886a19a03297555e.

For testing microversion in Tempest on gate, we need to set
a valid range of microversion in Tempest config and based on that
Tempest will run appropriate tests.

This commit adds the below range options for compute microversion testing-
- [None, 'latest'] - for master branch as default
- [None, None] - for tests running on v2.0
- option to set the range.

Depends-On: I81e86faca6f8c0ffb7da22154a62236ac25cf0c0

Partially implements blueprint api-microversions-testing-support

Change-Id: I171b862d1bba1af467f5b9a76288216c39e2adda

dtroyer/devstack,nawawi/openstack,Mahito/devstack,dtroyer/devstack,avvocatodemarchis/devstack,avvocatodemarchis/devstack,bswartz/devstack,openstack-dev/devstack,richliu/devstack,group-policy/devstack,Mahito/devstack,dirkmueller/devstack,openstack-dev/devstack,bigswitch/devstack,noironetworks/devstack,mssumanth/devstack,mssumanth/devstack,bswartz/devstack,varunarya10/devstack,samgoon/devstack,richliu/devstack,dirkmueller/devstack,bigswitch/devstack,nawawi/openstack,samgoon/devstack,group-policy/devstack,noironetworks/devstack,varunarya10/devstack