Fix build steps losing sort order after first poll delay

Summary: We have this very annoying bug when viewing steps, they get reordered after the poll delay (3 seconds). Basically the update which sorts them doesn't get called after polling, only on initialization so they lose order after 3 seconds.

Reviewers: vishal

Reviewed By: vishal

Subscribers: cramer

Projects: #changes

Differential Revision: https://tails.corp.dropbox.com/D79446