Fix double stringify

lib/modules/whisper/index.js

@@ -96,11 +96,11 @@ class Whisper {
     let connection = this.communicationConfig.connection || {};
 
     // todo: make the add code a function as well
-    let config = JSON.stringify({
+    let config = {
       server: canonicalHost(connection.host || defaultHost),
       port: connection.port || '8546',
       type: connection.type || 'ws'
-    });
+    };
 
     config = JSON.stringify(config);