[ARM] ping6 is not available in orchagent docker

[Blueve]

Description

The ping6 tool is available in amd64 build image but missing in armhf build image.

The base image doesn't explicitly install the iputils-ping for both amd64 and armhf, we guessing the tool might be installed as some packages' dependency in amd64 base image.

To solve the issue, we can explicitly install the package on the top of armhf base image.

Steps to reproduce the issue:

1. Attach to swss docker
2. Try invoke ping6

Describe the results you received:

No command found

Describe the results you expected:

ping6 result

Output of show version:

N/A

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

N/A