[test_show_ndp] Filter out arp entries with no MAC address

[lolyu]

Description of PR

As nbrshow only shows entries that has lldaddr, we need to enforce
same behavior to filter out entries without MAC address, to guarantee it
will be shown in the output of show ndp.

Signed-off-by: Longxiang Lyu lolv@microsoft.com

Summary:
Fixes # (issue)

Type of change

• Bug fix
• Testbed and Framework(new/improvement)
• Test case(new/improvement)

Approach

What is the motivation for this PR?

The output of ip neigh might contains FAILED entries like the following without lladdr:

fe80::2a99:3aff:fe17:1c8c dev Ethernet112  FAILED
fe80::2a99:3aff:fe17:1c8c dev Ethernet80  FAILED
fe80::2a99:3aff:fe17:1c8c dev Ethernet68  FAILED

And those entries will be excluded by nbrshow, which will be called by show nbr.
In this case, test_show_ndp will fail due to the failure to find a match for those FAILED arp entries.

How did you do it?

Let test_show_ndp only checks entries that has lladdr.

How did you verify/test it?

Test test_show_ndp

iface_namingmode/test_iface_namingmode.py::TestNeighbors::test_show_ndp[alias] PASSED                                                                                       [ 50%]
iface_namingmode/test_iface_namingmode.py::TestNeighbors::test_show_ndp[default] PASSED                                                                                     [100%]

Any platform specific information?

Arista 7060 T1

Supported testbed topology if it's a new test case?

Documentation