Add a test case for LLDP_LOC_CHASSIS.lldp_loc_man_addr has only one IPv6 address

[qiluo-msft]

Add a test case for LLDP_LOC_CHASSIS.lldp_loc_man_addr has only one IPv6 address.
This is a follow up issue for #164

Description

Steps to reproduce the issue:
1.
2.
3.

Describe the results you received:

Describe the results you expected:

Additional information you deem important (e.g. issue happens only occasionally):

**Output of `show version`:**

```
(paste your output here)
```

**Attach debug file `sudo generate_dump`:**

```
(paste your output here)
```