revert special handling of requested tenant when setting user info in thread context

Signed-off-by: Mark Boyd <[email protected]>

Author: markdboyd

src/main/java/org/opensearch/security/privileges/PrivilegesEvaluator.java

@@ -300,11 +300,7 @@ private void setUserInfoInThreadContext(PrivilegesEvaluationContext context) {
             joiner.add(escapePipe(String.join(",", context.getMappedRoles())));
 
             String requestedTenant = context.getUser().getRequestedTenant();
-            if (!Strings.isNullOrEmpty(requestedTenant)) {
-                joiner.add(escapePipe(requestedTenant));
-            } else {
-                joiner.add("null");
-            }
+            joiner.add(requestedTenant);
 
             String tenantAccessToCheck = getTenancyAccess(context);
             joiner.add(tenantAccessToCheck);