Starting from NSX version 2.5.1, LBService will have a new property
'relax_scale_validation'. If this flag is set to true, scale
validation for vs, pool, pool member and rule will be relaxed for lbs
Checks are added to prevent including this flag in API calls on older
versions of NSX backend. feature_supported for this new flag is added
in NsxLib for MP. For Policy, ResourceDef and LBServiceDef are
responsible for the checks.
For MP, checks are added in _build_args() in load_balancer.py >
Service class so that the new flag is only passed when NSX meets
the version requirement.
For Policy, ResourceDef now has a new attribute nsx_version and two
new methods: _set_attr_if_supported() and _attr_supported().
get_obj_dict() will use them to check if a certain attr meets
version requirement, and only include it in body if true.
Change-Id: I4f9c3bfd7995bca85a51a6971fc9d784e574301a
093d510988