qemu: driver: Use appropriate job name when setting blockjob speed

qemuDomainBlockJobSetSpeed was not converted to get the job name from
the block job data. This means that after enabling blockdev the API call
would fail as we wouldn't use the appropriate name.

https://bugzilla.redhat.com/show_bug.cgi?id=1780497Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>

src/qemu/qemu_driver.c

@@ -17864,8 +17864,8 @@ qemuDomainBlockJobSetSpeed(virDomainPtr dom,
     virDomainDiskDefPtr disk;
     int ret = -1;
     virDomainObjPtr vm;
-    g_autofree char *device = NULL;
     unsigned long long speed = bandwidth;
+    g_autoptr(qemuBlockJobData) job = NULL;
 
     virCheckFlags(VIR_DOMAIN_BLOCK_JOB_SPEED_BANDWIDTH_BYTES, -1);
 
@@ -17895,12 +17895,15 @@ qemuDomainBlockJobSetSpeed(virDomainPtr dom,
     if (!(disk = qemuDomainDiskByName(vm->def, path)))
         goto endjob;
 
-    if (!(device = qemuAliasDiskDriveFromDisk(disk)))
+    if (!(job = qemuBlockJobDiskGetJob(disk))) {
+        virReportError(VIR_ERR_INVALID_ARG,
+                       _("disk %s does not have an active block job"), disk->dst);
         goto endjob;
+    }
 
     qemuDomainObjEnterMonitor(driver, vm);
     ret = qemuMonitorBlockJobSetSpeed(qemuDomainGetMonitor(vm),
-                                      device,
+                                      job->name,
                                       speed);
     if (qemuDomainObjExitMonitor(driver, vm) < 0)
         ret = -1;