Use ATTRIBUTE_FALLTHROUGH

Use ATTRIBUTE_FALLTHROUGH, introduced by commit
5d84f5961b, instead of comments to
indicate that the fall through is an intentional behavior.

Signed-off-by: Marc Hartmayer <mhartmay@linux.vnet.ibm.com>
Reviewed-by: Boris Fiuczynski <fiuczy@linux.vnet.ibm.com>
Reviewed-by: Bjoern Walk <bwalk@linux.vnet.ibm.com>

tools/virsh-domain.c

@@ -2504,14 +2504,14 @@ virshBlockJobInfo(vshControl *ctl,
             switch (last_error->code) {
             case VIR_ERR_INVALID_ARG:
                 priv->blockJobNoBytes = true;
-                /* fallthrough */
+                ATTRIBUTE_FALLTHROUGH;
             case VIR_ERR_OVERFLOW:
                 if (!bytes && !raw) {
                     /* try again with MiB/s, unless forcing bytes */
                     vshResetLibvirtError();
                     break;
                 }
-                /* fallthrough */
+                ATTRIBUTE_FALLTHROUGH;
             default:
                 goto cleanup;
             }