CLC-3186: LiveUpdates: Start doing warmups earlier

https://jira.media.berkeley.edu/jira/browse/CLC-3186

Start doing warmups earlier.
Trigger warmup from BootstrapController as soon as we know we have a valid session[:user_id]
Merge pull request #2064 from chikoon/CLC-3186-start-warmups-early

CLC-3186: LiveUpdates: Start doing warmups earlier