don't use default rg in test

[changlong-liu]

No description provided.

[qiaozha]

which issue is this PR trying to resolve.
If the list command has two operation listbysubscription and listbyresourcegroup inside it. -g "" will only test the listbysubscription.
Is this what they wanted?

[changlong-liu]

Hi @qiaozha ,
It's for #337.
Yes, this PR add -g "" for those example don't provide any resourcegroup, so that we can explicitly tell that the test is for list-by-subscription.
If we need to test list-by-resource group, we can use the example in which a resourcegroup is provided.

[qiaozha]

okay, approved.