MultiSelect: selectionLimit causes options to be in disabled-state

[simplicitytrade]

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://stackblitz.com/edit/ngprime-multiselect-fa5cm2

Current behavior
I have set a selectionLimit. Once I open the dropdown, the options are disabled.

Expected behavior
I would expect the the options are selectable until the real "selectionLimit" is reached.

Minimal reproduction of the problem with instructions
Follow the stackblitz test link and take a look at the different cases. Once you open the dropdown you see the disabled options which should not have this state.

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

Please tell us about your environment:

• Angular version: 7.X

• PrimeNG version: 8.0.2

• Browser: all

• Language: all

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