Always run "behavior-populate" before "behavior-show-more"

Summary:
Ref T2009. This clears the stage for D11977.

Specifically, D11977 moves "show context" logic into ChangesetViewManager, but those objects won't exist if we don't run "behavior-populate" first.

Generally, this increases consistency across changeset views -- which is still very low overall, but getting slightly better.

Both of these should probably move up more and use ChangesetListView, but we don't need to do that quite yet.

Test Plan:

• Took changeset actions in Phriction diff view.
• Took changeset actions in Differential standalone view.
• Took changeset actions in normal Differential view.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T2009

Differential Revision: https://secure.phabricator.com/D11978