[minigraph_facts] support PortChannel inside Vlan, improve module fail message

[qiluo-msft]

Description of PR

If there is PortChannel inside Vlan, original code with throw and the module will fail with a short message like

E           RunAnsibleModuleFail: run module minigraph_facts failed, Ansible Results =>
E           {
E               "changed": false,
E               "failed": true,
E               "invocation": {
E                   "module_args": {
E                       "filename": null,
E                       "host": "str-msn2700-20"
E                   }
E               },
E               "msg": "PortChannel101"
E           }

Type of change

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

Approach

What is the motivation for this PR?

How did you do it?

How did you verify/test it?

Test vlan/test_vlan.py with

1. DUT SKU: Mellanox-SN2700-D48C8
2. topo: t0-56-po2vlan

Any platform specific information?

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

Documentation

[lgtm-com]

This pull request fixes 2 alerts when merging 1d96955 into 11ed1e7 - view on LGTM.com

fixed alerts:

• 2 for Unused local variable

[lgtm-com]

This pull request fixes 2 alerts when merging 45a73f0 into 42bbc2e - view on LGTM.com

fixed alerts:

• 2 for Unused local variable