[pytest]: add EosHost for neighbor devices

[lguohan]

also use eos_facts to check eos neighbor device health

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@1cafe0c9f994:/data/tests$ py.test --inventory veos.vtb --host-pattern all --user admin -vvv --show-capture stdout --testbed vms-kvm-t0 --testbed_file vtestbed.csv --disable_loganalyzer --log-file ~/abc.log --log-level debug test_nbr_health.py | 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/tests, inifile: pytest.ini
plugins: ansible-2.2.2
collecting ... collected 1 item

test_nbr_health.py::test_neighbors_health PASSED                         [100%]

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

Any platform specific information?

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

Documentation

[lguohan]

@wangxin to review