Description
When config_db.json does not have DEVICE_NEIGHBOR_METADATA, the BGP neighbor configurations present in config_db.json are not pushed to FRR.

The dependency on device_neighbor_metadata was introduced in this pull request
https://github.com/Azure/sonic-buildimage/pull/3694/files
Steps to reproduce the issue:

1. Add BGP neighbor entries in config_db.json
2. Do not add DEVICE_NEIGHBOR_METADATA
3. Set docker_routing_config_mode as 'unified' or 'separated'

Describe the results you received:

Describe the results you expected:

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

**Output of `show version`:**

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**Attach debug file `sudo generate_dump`:**

```
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