[bgp_facts]: fix num_npus param bug

[lguohan]

if test does not pass num_npus param, the default value is None

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 -vvv --inventory veos.vtb --host-pattern all --user admin --testbed vms-kvm-t0 --testbed_file vtestbed.csv --disable_loganalyzer --show-capture stdout test_bgp_speaker.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 2 items 

test_bgp_speaker.py::test_bgp_speaker_bgp_sessions PASSED                [ 50%]
test_bgp_speaker.py::test_bgp_speaker_announce_routes[True-False-1514] PASSED [100%]

Any platform specific information?

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

Documentation