Verify connection to Elasticsearch (#1487) (#1497)

Co-authored-by: Tomas Della Vedova <delvedor@users.noreply.github.com>

index.js

@@ -255,6 +255,10 @@ class Client extends ESAPI {
     }
 
     const client = new Client(options)
+    // sync product check
+    const tSymbol = Object.getOwnPropertySymbols(this.transport)
+      .filter(symbol => symbol.description === 'product check')[0]
+    client.transport[tSymbol] = this.transport[tSymbol]
     // Add parent extensions
     if (this[kExtensions].length > 0) {
       this[kExtensions].forEach(({ name, opts, fn }) => {