PanelMenu animation broken on fast click

[marius-oprea]

I'm submitting a ... (check one with "x")

[x] bug report => Search github for a similar issue or PR before submitting
[ ] feature request => Please check if request is not on the roadmap already https://github.com/primefaces/primeng/wiki/Roadmap
[ ] support request => Please do not submit support request here, instead see http://forum.primefaces.org/viewforum.php?f=35

Plunkr Case (Bug Reports)
https://www.primefaces.org/primeng/#/panelmenu

http://plnkr.co/edit/VZbdZfQ7SuTV87tTkbYR?p=preview

Current behavior
On Chrome and Opera browser, if you expand and collapse the panel menu fast, the texts and icons overlaps

Expected behavior
On Chrome browser, the panel menu should expand/collapse without overlapping texts and icons

Minimal reproduction of the problem with instructions

• access your documentation page for panel menu on Chrome and Opera browser
  https://www.primefaces.org/primeng/#/panelmenu
  -play with the demo menu(it behave the same with other examples too) by expanding/collapsing.
• notice the overlapping of texts and icons

What is the motivation / use case for changing the behavior?

Please tell us about your environment:
Chrome, Opera browsers the latest version

• Angular version: 2.0.X

• PrimeNG version: 2.0.X

• Browser: [all | Chrome XX | Firefox XX | IE XX | Safari XX | Mobile Chrome XX | Android X.X Web Browser | iOS XX Safari | iOS XX UIWebView | iOS XX WKWebView ]

• Language: [all | TypeScript X.X | ES6/7 | ES5]

• Node (for AoT issues): node --version =