Description of problem:
Create a VM by virsh define xml_path && virsh start $vm_name, then attach a disk by "virsh attach-disk --domain subVmTest1 --source $disk_path --target vdc --targetbus virtio", then switch to the VM detail page, remove the disk which is attached above, the disk can not be removed

Version-Release number of selected components (if applicable):
cockpit-234-1.el8.ppc64le
cockpit-machines-234-1.el8.noarch
libvirt-dbus-1.3.0-2.module+el8.3.0+6423+e4cb6418.ppc64le

How reproducible:
100%

Steps to Reproduce:
1. Create a VM by virsh define xml_path && virsh start $vm_name
2. Attach a disk by "virsh attach-disk --domain subVmTest1 --source $disk_path --target vdc --targetbus virtio"
3. Go to the VM detail page, removed the disk which is attached in step 2

Actual results:
1. After step 3, the disk can not be removed

Expected results:
1. The disk can be removed after clicking removed button on the Page

Additional info:
1. If shutting off the VM after step 3, the disk is removed