`get_bgp_config()` fails to process NHS on Arista 7150S

[bewing]

If NHS is set on a peer-group, it is incorrectly reported in the peer group, and the correct value is not propagated down into the peer itself.

In [5]: with EOSDriver("ROUTER01", "bewing", getpass()) as d:
   ...:     pprint(d.get_bgp_config())
   ...:     print(d.get_facts()["os_version"])
   ...:
Password:
{'PEER-GROUP1': {'apply_groups': [],
                  'description': '',
                  'export_policy': 'PEER-GROUP1-OUT',
                  'import_policy': '',
                  'local_address': '',
                  'local_as': 65501,
                  'multihop_ttl': 0,
                  'multipath': False,
                  'neighbors': {'10.253.0.1': {'authentication_key': '',
                                               'description': 'ROUTER03',
                                               'export_policy': '',
                                               'import_policy': '',
                                               'local_address': '',
                                               'local_as': 65501,
                                               'nhs': False,
                                               'prefix_limit': {},
                                               'remote_as': 65503,
                                               'route_reflector_client': False},
                                '10.253.0.3': {'authentication_key': '',
                                               'description': 'ROUTER02',
                                               'export_policy': '',
                                               'import_policy': '',
                                               'local_address': '',
                                               'local_as': 65501,
                                               'nhs': False,
                                               'prefix_limit': {},
                                               'remote_as': 65502,
                                               'route_reflector_client': False},
                                '10.253.4.97': {'authentication_key': '',
                                                'description': 'FIREWALL01',
                                                'export_policy': '',
                                                'import_policy': '',
                                                'local_address': '',
                                                'local_as': 65501,
                                                'nhs': False,
                                                'prefix_limit': {},
                                                'remote_as': 65599,
                                                'route_reflector_client': False}},
                  'nhs': True,
                  'prefix_limit': {},
                  'remote_as': 0,
                  'remove_private_as': False,
                  'type': ''},
 'WAN-PEERS': {'apply_groups': [],
               'description': '',
               'export_policy': '',
               'import_policy': '',
               'local_address': '',
               'local_as': 65501,
               'multihop_ttl': 0,
               'multipath': False,
               'neighbors': {},
               'nhs': True,
               'prefix_limit': {},
               'remote_as': 0,
               'remove_private_as': False,
               'type': ''}
}
4.20.10M-2GB-10040268.42010M