fix #8807
fix #8807

Format the error of mount blob, return a http error so that the core can parse it.

Signed-off-by: wang yan <63b20dea16c07a874bc9bf767df5575676113cb6@vmware.com>

reasonerjt/harbor,wy65701436/harbor,reasonerjt/harbor,reasonerjt/harbor,reasonerjt/harbor,wy65701436/harbor,reasonerjt/harbor,wy65701436/harbor,wy65701436/harbor,wy65701436/harbor,wy65701436/harbor,reasonerjt/harbor