security: remove dead code from virSecurityDACGenLabel

* src/security/security_dac.c: remove useless dead code.
Signed-off-by: NAlex Jia <ajia@redhat.com>

src/security/security_dac.c

@@ -891,7 +891,6 @@ virSecurityDACGenLabel(virSecurityManagerPtr mgr,
     case VIR_DOMAIN_SECLABEL_NONE:
         /* no op */
         return 0;
-        break;
     default:
         virReportError(VIR_ERR_INTERNAL_ERROR,
                        _("unexpected security label type '%s'"),