fix unit test

Author: scottinet

src/kuzzle.js

@@ -538,7 +538,7 @@ Kuzzle.prototype.logout = function (cb) {
   });
 
   self.unsetJwtToken();
-  
+
   return self;
 };
 

test/kuzzle/constructor.test.js

@@ -913,7 +913,7 @@ describe('Kuzzle constructor', () => {
         kuzzle.login('local', loginCredentials);
       });
 
-      it('should have a empty token in logout callback', function (done) {
+      it('should have a empty token in logout callback', function () {
         var
           unsetJwtToken = false,
           kuzzle;
@@ -932,10 +932,8 @@ describe('Kuzzle constructor', () => {
           cb(null, {});
         };
 
-        kuzzle.logout(function() {
-          should(unsetJwtToken).be.exactly(true);
-          done();
-        });
+        kuzzle.logout(() => {});
+        should(unsetJwtToken).be.exactly(true);
       });
 
       it('should give an error if login query fail to the logout callback if is set', function (done) {