[AKS] BREAKING CHANGE: Change default VM size changes to "" and clear test cases#8736

zhoxing-ms merged 2 commits intoAzure:mainAzure/azure-cli-extensions:mainfrom

FumingZhang:fuming/aks-fix-0512FumingZhang/azure-cli-extensions:fuming/aks-fix-0512Copy head branch name to clipboard