Make tfstate sanitization jq query more resource-specific

[bronius]

In his enthusiasm to close merge 3d35327, @bronius would like to have made

...del(.resources[].instances[].attributes [
        "primary_access_key",
        "primary_connection_string",
        "primary_blob_connection_string",
        "secondary_access_key",
        "secondary_connection_string",
        "secondary_blob_connection_string"
      ])...

specific to the resource whose secrets we want to wipe from tfstate. Currently, it will take all Azure storage managed by the terraform implementing this module; It will be safer to limit to just something like ....resources[name=azurerm_storage_account.tfstate.name]....