CLDSRV-625: No scality-kms warning if not conf

Avoid print the warning if scality-kms is not configured:

```json
{"name":"S3","time":1742220545805,"error":{"code":"MODULE_NOT_FOUND","requireStack":["/home/mickael/scality/cloudserver/lib/kms/wrapper.js","/home/mickael/scality/cloudserver/lib/data/wrapper.js","/home/mickael/scality/cloudserver/lib/utilities/healthcheckHandler.js","/home/mickael/scality/cloudserver/lib/utilities/internalHandlers.js","/home/mickael/scality/cloudserver/lib/server.js","/home/mickael/scality/cloudserver/index.js"]},"level":"warn","message":"scality kms unavailable. Using file kms backend unless mem specified.","hostname":"mickael-xps","pid":139701}
```

Author: BourgoisMickael

lib/kms/wrapper.js

@@ -12,19 +12,24 @@ const Common = require('./common');
 const vault = require('../auth/vault');
 const Cache = require('./Cache');
 const cache = new Cache();
-let scalityKMS;
-let scalityKMSImpl;
-try {
-     // eslint-disable-next-line import/no-unresolved
-    const ScalityKMS = require('scality-kms');
-    scalityKMS = new ScalityKMS(config.kms);
-    scalityKMSImpl = 'scalityKms';
-} catch (error) {
-    logger.warn('scality kms unavailable. ' +
-      'Using file kms backend unless mem specified.',
-      { error });
-    scalityKMS = file;
-    scalityKMSImpl = 'fileKms';
+
+function getScalityKms() {
+    let scalityKMS;
+    let scalityKMSImpl;
+
+    try {
+        // eslint-disable-next-line import/no-unresolved
+        const ScalityKMS = require('scality-kms');
+        scalityKMS = new ScalityKMS(config.kms);
+        scalityKMSImpl = 'scalityKms';
+    } catch (error) {
+        logger.warn('scality kms unavailable. ' +
+        'Using file kms backend unless mem specified.',
+        { error });
+        scalityKMS = file;
+        scalityKMSImpl = 'fileKms';
+    }
+    return { scalityKMS, scalityKMSImpl };
 }
 
 let client;
@@ -37,8 +42,7 @@ if (config.backends.kms === 'mem') {
     client = file;
     implName = 'fileKms';
 } else if (config.backends.kms === 'scality') {
-    client = scalityKMS;
-    implName = scalityKMSImpl;
+    ({ scalityKMS: client, scalityKMSImpl: implName } = getScalityKms());
 } else if (config.backends.kms === 'kmip') {
     const kmipConfig = { kmip: config.kmip };
     if (!kmipConfig.kmip) {