CLDSRV-839: Limit warning to valid requests

S3 can receive many invalid requests, from internet scraper or other things.
We don't want to warn for a request we can't process.

Example warnings from lab / tests
- apiMethod=undefined, method=OPTIONS, url=/bucketcorstester
- apiMethod=undefined, method=POST, url=/
- apiMethod=undefined, method=DELETE, url=/bucketA
- apiMethod=undefined, method=PUT, url=/as
- apiMethod=undefined, method=PUT, url=/xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
- apiMethod=undefined, method=PUT, url=/192.168.5.4
- apiMethod=undefined, method=PUT, url=/.myawsbucket
- apiMethod=undefined, method=PUT, url=/myawsbucket.
- apiMethod=undefined, method=PUT, url=/my..examplebucket
- apiMethod=undefined, method=PUT, url=/my.%23s3bucket

Author: BourgoisMickael

lib/utilities/serverAccessLogger.js

@@ -297,11 +297,16 @@ function getOperation(req) {
     }
 
     if (!resourceType) {
-        process.emitWarning('Unknown apiMethod for server access log', {
-            type: 'ServerAccessLogWarning',
-            code: 'UNKNOWN_API_METHOD',
-            detail: `apiMethod=${req.apiMethod}, method=${req.method}, url=${req.url}`
-        });
+        // Only emit a warning if apiMethod is not undefined, meaning request is valid.
+        // Otherwise we could get spam by invalid or broken requests.
+        // To help catch missing valid operation.
+        if (req.apiMethod) {
+            process.emitWarning('Unknown apiMethod for server access log', {
+                type: 'ServerAccessLogWarning',
+                code: 'UNKNOWN_API_METHOD',
+                detail: `apiMethod=${req.apiMethod}, method=${req.method}, url=${req.url}`
+            });
+        }
         return `REST.${req.method}.UNKNOWN`;
     }