[yang-models] device_metadata validation issue

[ganglyu]

Description

'DEVICE_METADATA': {'localhost': {'bgp_asn': '65100',
'cloudtype': None,
'deployment_id': None,
'docker_routing_config_mode': 'separated',
'hostname': 'multi_npu_platform_01',
'hwsku': 'multi-npu-01',
'region': None,
'synchronous_mode': 'enable',
'type': 'LeafRouter'}},

Config db schema generated by minigraph can’t pass yang validation, deployment_id can’t be none for yang validation.
parse_asic_meta did not update deployment_id, and it seems that we need to update yang model or sonic-config-engine.

Steps to reproduce the issue:

1. Run command 'sonic-cfggen -m tests/multi_npu_data/sample-minigraph-noportchannel.xml -p tests/multi_npu_data/sample_port_config-3.ini -n asic3 --print-data'
2. Use sonic_yang to validate config db schema.

Describe the results you received:

Yang validation failed.

Describe the results you expected:

Yang validation should pass.

Output of show version:

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Output of show techsupport:

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

[SuvarnaMeenakshi]

@ganglyu deployment_id is specified as int value, so ideally should not be None.
Fix should be made in sonic-cfggen to ensure that deployment id is not populated if it is None.

@arlakshm fyi