Routing application split config support

[nikos-github]

Enabling support for routing application (frr) split configuration.

The changes are backwards compatible with existing configurations.

To enable split configuration, the following field needs to be added to the device metadata, followed by a config reload -y:

"DEVICE_METADATA": {
    "localhost": {
        "hwsku": "Force10-Z9100", 
        "hostname": "sonic", 
        "platform": "x86_64-dell_z9100_c2538-r0", 
        "mac": "54:bf:64:ce:c0:40",
        "docker_routing_config_mode": "split",          <===== new field 
        "bgp_asn": "65100", 
        "type": "LeafRouter"
    }
}, 

The field is optional and can take two values: unified and split. The absence of the field, implicitly means the value is unified. Changes to the field must be followed by a config reload -y at this point.

Signed-off-by: nikos ntriantafillis@gmail.com

[nikos-github]

@lguohan Please review.

[jipanyang]

Could you please update DEVICE_METADATA schema with your changes to the Configuration DB schema section of https://github.com/Azure/sonic-swss/blob/master/doc/swss-schema.md ?

[nikos-github]

@jipanyang I'd be happy to update the schema after the change is signed off here. I don't see a DEVICE_METADATA section though. I assume you want me to add one to indicate this change? Please clarify.

[jipanyang]

@nikos-github if possible, please push all fields being used for DEVICE_METADATA, but putting whatever you added is also a good start. thanks!