[Interactive] Fix #16931: Fix KeyError in az interactive --update

[fengzhou-msft]

Description

Resolve #16931

interactive is written in a special way that it is an azure-cli module, but it will install the interative extension for starting an interactive shell. With the use of command index, interactive command group only loads the interactive module and not azext_interactive module as the extension has 0 command. That's why reload_module will throw KeyError when trying to reload azext_interactive after updated.

This PR adds check whether the module is already imported before reloading it.

Testing Guide

1. Install an old version of interactive
az extension add --upgrade -n interactive --version 0.4.3
2. Run the command to update interactive
az interactive --update

History Notes

[Component Name 1] BREAKING CHANGE: az command a: Make some customer-facing breaking change.
[Component Name 2] az command b: Add some customer-facing feature.

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[jiasli]

How about we put the try except clause in

azure-cli/src/azure-cli/azure/cli/command_modules/interactive/custom.py

Line 27 in 222e501

reload_extension(INTERACTIVE_EXTENSION_NAME)

az interactive should be responsible for non-existing extension, such as ExtensionNotInstalledException.