[Backport 2.x] Change log message from warning to trace on WWW-Authenticate challenge (#3446)

Backport a41638b from #3364.

Signed-off-by: Priyank Bagrecha <pbagrecha@roku.com>
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: Priyank Bagrecha <pbagrecha@roku.com>

Author: 3 people

src/main/java/org/opensearch/security/auth/BackendRegistry.java

@@ -281,7 +281,9 @@ && isBlocked(((InetSocketAddress) request.getHttpChannel().getRemoteAddress()).g
 
                 if (authDomain.isChallenge() && httpAuthenticator.reRequestAuthentication(channel, null)) {
                     auditLog.logFailedLogin("<NONE>", false, null, request);
-                    log.warn("No 'Authorization' header, send 401 and 'WWW-Authenticate Basic'");
+                    if (isTraceEnabled) {
+                        log.trace("No 'Authorization' header, send 401 and 'WWW-Authenticate Basic'");
+                    }
                     return false;
                 } else {
                     // no reRequest possible