qemu: Don't error out if allocation info can't be queried

qemuDomainGetBlockInfo would error out if qemu did not report
'wr_highest_offset'. This usually does not happen, but can happen
briefly during active layer block commit. There's no need to report the
error, we can simply report that the disk is fully alocated at that
point.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1452045

src/qemu/qemu_driver.c

@@ -11553,14 +11553,6 @@ qemuDomainGetBlockInfo(virDomainPtr dom,
     }
 
     if (!entry->wr_highest_offset_valid) {
-        if (virStorageSourceGetActualType(disk->src) == VIR_STORAGE_TYPE_BLOCK &&
-            disk->src->format != VIR_STORAGE_FILE_RAW) {
-            virReportError(VIR_ERR_INTERNAL_ERROR,
-                           _("failed to query the maximum written offset of "
-                             "block device '%s'"), disk->dst);
-            goto endjob;
-        }
-
         info->allocation = entry->physical;
     } else {
         if (virStorageSourceGetActualType(disk->src) == VIR_STORAGE_TYPE_FILE &&