Fix exception in fdb.py caused by IPv6 Address in vlan interfaces

[bingwang-ms]

Description of PR

Summary:
Fixes # (issue)
PR #1982 added IPv6 address to vlan interface, which caused
regression in test_fdb_mac_expire. This commit is to address this issue.

Type of change

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

Approach

What is the motivation for this PR?

PR #1982 added IPv6 address to vlan interface. As a result, the config file /root/fdb_info.txt for test_fdb_mac_expire is misformatted, which will cause exception in fdb.py. This PR is to address this issue.

How did you do it?

Update the template for generating /root/fdb_info.txt, and only IPv4 address is included in the generated config file.

How did you verify/test it?

Verify it on Arista-7260

========================================================================================= test session starts =========================================================================================
platform linux2 -- Python 2.7.12, pytest-4.6.5, py-1.8.1, pluggy-0.13.1 -- /usr/bin/python
cachedir: .pytest_cache
ansible: 2.8.7
rootdir: /data/Networking-acs-sonic-mgmt/tests, inifile: pytest.ini
plugins: forked-1.1.3, xdist-1.28.0, ansible-2.2.2, repeat-0.8.0
collected 1 item                                                                                                                                                                                      

fdb/test_fdb_mac_expire.py::TestFdbMacExpire::testFdbMacExpire 
------------------------------------------------------------------------------------------- live log setup --------------------------------------------------------------------------------------------
06:36:30 INFO __init__.py:set_default:14: Completeness level not set during test execution. Setting to default level: CompletenessLevel.basic
06:36:30 INFO __init__.py:check_test_completeness:128: Test has no defined levels. Continue without test completeness checks
06:36:36 INFO ptfhost_utils.py:copy_ptftests_directory:47: Copy PTF test files to PTF host 'vms7-7'
06:36:51 INFO test_fdb_mac_expire.py:copyFdbInfo:134: Copying fdb_info.txt config file to vms7-7
06:36:56 INFO __init__.py:loganalyzer:15: Log analyzer is disabled
-------------------------------------------------------------------------------------------- live log call --------------------------------------------------------------------------------------------
06:36:59 INFO test_fdb_mac_expire.py:__runPtfTest:90: Running PTF test case 'fdb_mac_expire_test.FdbMacExpireTest' on 'vms7-7'
06:37:04 INFO test_fdb_mac_expire.py:testFdbMacExpire:236: wait for FDB aging time of '60' secs
06:38:24 INFO test_fdb_mac_expire.py:testFdbMacExpire:248: MAC table entries count: 112, after 75 sec
06:38:41 INFO test_fdb_mac_expire.py:testFdbMacExpire:248: MAC table entries count: 112, after 90 sec
06:38:57 INFO test_fdb_mac_expire.py:testFdbMacExpire:248: MAC table entries count: 0, after 105 sec
PASSED                                                                                                                                                                                          [100%]
------------------------------------------------------------------------------------------ live log teardown ------------------------------------------------------------------------------------------
06:39:01 INFO ptfhost_utils.py:copy_ptftests_directory:52: Delete PTF test files from PTF host 'vms7-7'


------------------------------------------------------------------ generated xml file: /data/Networking-acs-sonic-mgmt/tests/tr.xml -------------------------------------------------------------------
===================================================================================== 1 passed in 151.10 seconds ======================================================================================

Any platform specific information?

No

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

N/A

Documentation

N/A

[neethajohn]

Is #2109 trying to address the same issue?

[yxieca]

@bingwang-ms please resolve the merge conflict.

[bingwang-ms]

Already fixed in #2109