aks-preview extension release v0.4.19

[bingosummer]

---

This checklist is used to make sure that common guidelines for a pull request are followed.

General Guidelines

• Have you run azdev style <YOUR_EXT> locally? (pip install azdev required)
• Have you run python scripts/ci/test_index.py -q locally?

For new extensions:

• My extension description/summary conforms to the Extension Summary Guidelines.

[azuresdkci]

If this PR is for a new extension or change to an existing extension, use the following to try out the changes in this PR:

docker run -it microsoft/azure-cli:latest
export EXT=<NAME>
pip install --upgrade --target ~/.azure/cliextensions/$EXT "git+https://github.com/bingosummer/azure-cli-extensions.git@aks#subdirectory=src/$EXT&egg=$EXT"

[bingosummer]

@zikalino @zqingqing1 please have a look.

[zikalino]

@bingosummer no need to have 2 entries in index.json, you can remove the old one
just to make sure you can compare them to make sure there's nothing specific the new entry is using.

we usually can have 2 entries, if the new release doesn't support some older version of Azure CLI core, and I think it's not the case here.

[bingosummer]

@bingosummer no need to have 2 entries in index.json, you can remove the old one
just to make sure you can compare them to make sure there's nothing specific the new entry is using.

we usually can have 2 entries, if the new release doesn't support some older version of Azure CLI core, and I think it's not the case here.

@zikalino Got your point. Have removed the old one.

[bingosummer]

@zikalino Thanks for your kindly review!
Just out of curiosity, if we keep only the latest version in index.json, can customers install the old versions of extension?