Error Detaching Volume on GlusterFS Primary Storage

##### ISSUE TYPE
* Bug Report

##### COMPONENT NAME

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Primary Storage (GlusterFS)
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##### CLOUDSTACK VERSION

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4.17.1.0
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##### CONFIGURATION

##### OS / ENVIRONMENT

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CentOS Linux 7 (Core)
qemu-img version 2.12.0
glusterfs 6.1

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##### SUMMARY

Can't detach volumes created on GlusterFS primary storage from VM. Tested on two different cloudstack installations. Everything works fine with other primary storage types. The volume can be detached and removed if the VM status is stopped but not when running.

##### STEPS TO REPRODUCE

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- Create GlusterFS Primary Storage with tag
- Create Disk Offering that uses just crated GlusterFS Primary Storage's tag.
- Create Volume using just created Disk Offering
- Attach Volume to VM
- Detach Volume from VM

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##### EXPECTED RESULTS

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- Success detaching Volume

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##### ACTUAL RESULTS

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- (test-detach) Failed to detach volume test-detach from VM test-vm-for-gluster ; com.cloud.exception.InternalErrorException: disk: /mnt/b440b605-a876-35f8-be84-2b5696650654/5605035d-e060-42a6-89a1-6f9c949463fc is not attached before

~~~

首先，在執行中的 VM 上使用 GlusterFS 作為主要儲存，並使用列出的 CentOS、qemu-img 和 glusterfs 環境，重現 issue 中描述的 detach 流程。追蹤「is not attached before」錯誤的來源，並將其與其他主要儲存類型進行比較。當 VM 執行時 volume 能夠成功 detach，且回報的情境已由回歸測試涵蓋時，即表示完成。

由索引模型根據 Issue 內容生成。