[RouteUpdater]: Fix multi_asic mock function implementation and multi_asic variable name

[SuvarnaMeenakshi]

[RouteUpdater]: Fix multi_asic mock function implementation.
Update multi_asic mock function to return port_table from config_db
was returning empty dictionary due to which RouteUpdater class
was not completely unit-tested as one of the condition check was
never set to true.

Signed-off-by: Suvarna Meenakshi sumeenak@microsoft.com

- What I did

1. Fix multi_asic mock function implementation to get port_table information. There was a mistake in mock_get_port_table function due to which port_table was always empty dictionary.
2. Use multi_asic.get_port_table_for_asic() function as we require port_table only of a specific namespace and do not require the entire port_table.
3. Fix the incorrect multi_asic variable name used in RouteUdpater.
   Provides fix for 'sonic_py_common.multi_asic' has no attribute 'ROLE'" error message #188

- How I did it

1. Update multi_asic mock_get_port_table_for_asic implementation.
2. Fix the incorrect multi_asic variable name used in RouteUdpater.

- How to verify it
Load updated docker and query 1.3.6.1.2.1.4.24 MIB. Verify the result.
"AttributeError: module 'sonic_py_common.multi_asic' has no attribute 'ROLE'" error message should not be seen in syslog .

- Description for the changelog

[svc-acs]

Can one of the admins verify this patch?

[qiluo-msft]

[](start = 86, length = 1)

Remove trailing blank char. #Closed

[SuvarnaMeenakshi]

Updated as per comment.

[qiluo-msft]

If if statement is line breaked, you may add more indentation to them, so the branch code block is easier to find. There is a PEP. #Closed

[SuvarnaMeenakshi]

Updated as per comment.

[abdosi]

@SuvarnaMeenakshi INTERNAL_PORT is already present in mock db ?

[SuvarnaMeenakshi]

@SuvarnaMeenakshi INTERNAL_PORT is already present in mock db ?

yes, for example: https://github.com/Azure/sonic-snmpagent/blob/381ae478a6cb9f99e150406ed68cb672207bbddc/tests/mock_tables/asic0/config_db.json#L21
The mock_table's Role is not used to determine if a port channel is internal or not, to make the mock functions simpler, I have added a list of internal PortChannels here: https://github.com/Azure/sonic-snmpagent/blob/master/tests/mock_tables/multi_asic.py#L9
Also, there is a unit-test case to check if have an route through internal interface:
https://github.com/Azure/sonic-snmpagent/blob/381ae478a6cb9f99e150406ed68cb672207bbddc/tests/namespace/test_forward.py#L134