qemu: driver: Don't call qemuDomainDetermineDiskChain on block jobs

Our code calls it when starting or re-starting the domain or when
hotplugging the disk so there's nothing to be detected.

src/qemu/qemu_driver.c

@@ -16525,9 +16525,6 @@ qemuDomainBlockCopyCommon(virDomainObjPtr vm,
         goto endjob;
     }
 
-    if (qemuDomainDetermineDiskChain(driver, vm, disk, false, true) < 0)
-        goto endjob;
-
     /* clear the _SHALLOW flag if there is only one layer */
     if (!disk->src->backingStore)
         flags &= ~VIR_DOMAIN_BLOCK_COPY_SHALLOW;
@@ -16907,8 +16904,6 @@ qemuDomainBlockCommit(virDomainPtr dom,
 
     if (qemuDomainDiskBlockJobIsActive(disk))
         goto endjob;
-    if (qemuDomainDetermineDiskChain(driver, vm, disk, false, true) < 0)
-        goto endjob;
 
     if (!top)
         topSource = disk->src;