Validate service offering name for ( Compute, System, Disk offerings)

### The required feature described as a wish

Currently cloudstack is allowing to create offering with the same name for Compute, System, Disk offerings

Where as Cloudstack validates name for (Backup , Network and VPC offerings )

for compute offerings we can have the same name

Expected behaviour

It would be great if Cloudstack can validate the service offering name for Compute, System, Disk offerings in order to maintain consistency across

先找出現有的 Backup、Network 和 VPC offering 名稱驗證，接著追蹤 Compute、System 和 Disk offering 的建立路徑。比較這些行為，並為重複名稱新增 coverage；完成的標準是這些 offering 類型能如描述一致地拒絕重複項目。

由索引模型根據 Issue 內容生成。