qemu: error out on attempt to change blkiotune group name

Check that the attribute is the same in qemuDomainDiskChangeSupported
in case somebody tries to change it using the UpdateDevice API.

https://bugzilla.redhat.com/show_bug.cgi?id=1601677Signed-off-by: NJán Tomko <jtomko@redhat.com>
Reviewed-by: NLaine Stump <laine@laine.org>

src/qemu/qemu_domain.c

@@ -9397,6 +9397,8 @@ qemuDomainDiskChangeSupported(virDomainDiskDefPtr disk,
     CHECK_EQ(blkdeviotune.size_iops_sec,
              "blkdeviotune size_iops_sec",
              true);
+    CHECK_STREQ_NULLABLE(blkdeviotune.group_name,
+                         "blkdeviotune group name");
 
     if (disk->serial && STRNEQ_NULLABLE(disk->serial, orig_disk->serial)) {
         virReportError(VIR_ERR_OPERATION_UNSUPPORTED,