shared: explicitly ignore return value of g_utf8_validate()

Coverity doesn't like us ignoring the return value, although
we really only care about the "p" output pointer.

Try casting the result to (void), maybe that silences Coverity.

shared/nm-glib-aux/nm-shared-utils.c

@@ -1939,7 +1939,7 @@ nm_utils_buf_utf8safe_escape (gconstpointer buf, gssize buflen, NMUtilsStrUtf8Sa
 			break;
 
 		s = &p[1];
-		g_utf8_validate (s, buflen, &p);
+		(void) g_utf8_validate (s, buflen, &p);
 	} while (TRUE);
 
 	*to_free = g_string_free (gstr, FALSE);