Use the new NSO 6.0 HA terms
Master/slave have been renamed to primary/secondary. The configuration
model was changed in a backwards incompatible way, but the operational
state data is available in a new YANG module with the tfnm2
prefix.
I also fixed the version range check for deciding which HA test flavor to run. As it was it skipped HA on 6.0 altogether, until we would add 6.4