[pytest/lacp]: use lacp timer if lacp rate cmd is not available

[lguohan]

Description of PR

Summary:
Fixes #2041

Type of change

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

Approach

What is the motivation for this PR?

eos has deprecated lacp rate cmd in latest eos

Signed-off-by: Guohan Lu [email protected]

How did you do it?

use lacp timer if lacp rate cmd is not available

How did you verify/test it?

lgh@54edb99ee27f:/var/src/sonic-mgmt/tests$ ./run_tests.sh -i veos_vtb -d vlab-01 -n vms-kvm-t0 -f vtestbed.csv -k debug -l warning -m individual -q 1 -a False -e --disable_loganalyzer -u -c pc/test_lag_2.py -p logs
=== Running tests individually ===
/usr/local/lib/python2.7/dist-packages/ansible/parsing/vault/__init__.py:44: CryptographyDeprecationWarning: Python 2 is no longer supported by the Python core team. Support for it is now deprecated in cryptography, and will be removed in a future release.
  from cryptography.exceptions import InvalidSignature
================================================================================================= test session starts ==================================================================================================
platform linux2 -- Python 2.7.17, pytest-4.6.5, py-1.9.0, pluggy-0.13.1
ansible: 2.8.12
rootdir: /var/src/sonic-mgmt/tests, inifile: pytest.ini
plugins: forked-1.3.0, xdist-1.28.0, metadata-1.10.0, html-1.22.1, repeat-0.8.0, ansible-2.2.2
collected 3 items                                                                                                                                                                                                      

pc/test_lag_2.py::test_lag[unknown|unknown-single_lag] PASSED                                                                                                                                                    [ 33%]
pc/test_lag_2.py::test_lag[unknown|unknown-lacp_rate] PASSED                                                                                                                                                     [ 66%]
pc/test_lag_2.py::test_lag[unknown|unknown-fallback] SKIPPED                                                                                                                                                     [100%]

------------------------------------------------------------------------- generated xml file: /var/src/sonic-mgmt/tests/logs/pc/test_lag_2.xml -------------------------------------------------------------------------
=============================================================================================== short test summary info ================================================================================================
SKIPPED [1] /var/src/sonic-mgmt/tests/common/helpers/assertions.py:13: Skip fallback for lag PortChannel0001 due to fallback was not set for it
======================================================================================== 2 passed, 1 skipped in 1041.82 seconds ========================================================================================
lgh@54edb99ee27f:/var/src/sonic-mgmt/tests$ 

Any platform specific information?

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

Documentation