Preview Users UI bugs

[RidhamShah]

Describe the bugs
There are various UI bugs for Preview Users

• Preview Users data not loading on Preview Users Tab
• Data not loading on hard refresh
• Scroll bar showing unnecessary on Preview-User list
• Scroll bar showing unnecessary on each preview-user while adding experiment-condition to assign
  
  

Expected behavior
The preview users should load the data on initialization.
On showing all experiment-condition assignments for a Preview-user the data should have an auto-height increment.
For adding assignments to a Preview-User only a vertical scroll bar should be present if it exceeds the height limit only.

Steps to reproduce
Create an experiment with the state as Preview
Add users for Preview in Preview-Users Menu.
Clicking on the Experiment Menu and then on Participants(Preview-User) the user data inserted won't be shown
Also hard refreshing the page the preview-users data won't be shown

[bcb37]

QA: Preview users are still not displayed the first time you load the page. Now you can make them appear by changing pages, as well as changing tabs - but they should also appear initially.