Follow-up from "Remove small container width"

The following discussion from gitlab-ce!19893 should be addressed:

• @annabeldunstone commented on a discussion: (+7 comments)

  Aha! Found the reason the empty div is there- https://gitlab.com/gitlab-org/gitlab-ce/commit/c306c6da20d3422664a6fda7f4b0e680b5c3db7e#100325bde5b22bc23433fd2db4eac0f8fc4bdfc1_11_10

  We should probably add the container class to the last_push partial