[sonic-config-engine] Yang validation for sonic-config-engine is blocked by sonic-bgp-voq-chassis-neighbor.yang

[ganglyu]

Description

I’m trying to merge this PR, and it will run Yang validation for sonic-config-engine unit test.
#9700
And I find the unit test is blocked by sonic-bgp-voq-chassis-neighbor.yang, and many test cases can’t satisfy this constraint.
https://github.com/Azure/sonic-buildimage/blob/master/src/sonic-yang-models/yang-models/sonic-bgp-voq-chassis-neighbor.yang#L57-L59
And related test cases are:
test_minigraph_storage_backend_subintf
test_minigraph_storage_backend_resource_type
test_minigraph_storage_backend_no_resource_type
test_var_json_data
test_minigraph_vxlan
test_minigraph_vnet
test_minigraph_vlans
test_minigraph_vlan_members
test_minigraph_vlan_interfaces
test_minigraph_sub_port_intf_sub
test_minigraph_sub_port_intf_resource_type_non_backend_tor
test_minigraph_sub_port_intf_resource_type
test_minigraph_sub_port_interfaces
test_minigraph_portchannels
test_minigraph_portchannel_interfaces
test_minigraph_interfaces
test_minigraph_extra_ethernet_interfaces
test_minigraph_ethernet_interfaces
test_minigraph_bgp_voq_chassis_peer
test_minigraph_bgp_mon

Steps to reproduce the issue:

1. Use my PR to build sonic-config-engine
2. Check unit test result.

Describe the results you received:

20 test cases failed.

Describe the results you expected:

All test cases should pass.

Output of show version:

(paste your output here)

Output of show techsupport:

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Additional information you deem important (e.g. issue happens only occasionally):