[pytest/lldp]: use neighbor mgmt ip from config db if it is not in lldp

[lguohan]

use neighbor mgmt ip from config db when neighbor device
does not send mgmt ip via lldp TLV

Signed-off-by: Guohan Lu gulv@microsoft.com

Description of PR

Summary:
Fixes # (issue)

Type of change

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

Approach

How did you do it?

How did you verify/test it?

johnar@be5ad9fb861f:/data/sonic-mgmt/tests$ ANSIBLE_LIBRARY=/data/sonic-mgmt/ansible/library/     py.test --inventory veos.vtb --host-pattern all --user admin -vvv --show-capture stdout --testbed vms-kvm-t0             --testbed_file vtestbed.csv --disable_loganalyzer test_lldp.py::test_lldp_neighbor | tee ~/abc.txt
============================= test session starts ==============================
platform linux2 -- Python 2.7.12, pytest-4.6.9, py-1.8.1, pluggy-0.13.1 -- /usr/bin/python
cachedir: .pytest_cache
ansible: 2.8.7
rootdir: /data/sonic-mgmt/tests, inifile: pytest.ini
plugins: ansible-2.2.2
collecting ... collected 1 item

test_lldp.py::test_lldp_neighbor PASSED                                  [100%]

=============================== warnings summary ===============================

Any platform specific information?

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

Documentation