chimney script: add a prompt before deleting the previous blobber

currently, when a user runs chimney script, and if there any previous blobber its data will be erased without warning.

We if there is a previous blobber deployment, we should prompt the user and show a warning telling:
"A blobber already exists on this server. Do you wish to delete blobber currently deployed on this server [N/y]:"

在程式碼儲存庫中找到 chimney 腳本，很可能是一個處理 blobber 部署的 shell 腳本。找到它檢查現有 blobber 並刪除它的部分。使用 'read' 添加一個提示，在刪除前請求使用者確認。在本機測試腳本，確保警告出現且僅在輸入 'y' 或 'Y' 時繼續刪除。

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