show 'sign' usage for secret keys

Secret keys can be used for signing in algorithms like HMAC and
CMAC so they should display their CKA_SIGN attribute value
when listing object attributes

Fixes #2851

src/tools/pkcs11-tool.c

@@ -5199,7 +5199,7 @@ show_key(CK_SESSION_HANDLE sess, CK_OBJECT_HANDLE obj)
 		printf("%sdecrypt", sepa);
 		sepa = ", ";
 	}
-	if (!pub && getSIGN(sess, obj)) {
+	if ((!pub || sec) && getSIGN(sess, obj)) {
 		printf("%ssign", sepa);
 		sepa = ", ";
 	}