[diffusion] keep 'view' parameter when clicking on a line number

Summary:
Clicking on a line number will remove the current 'view' the user is in.

This patch retains the current view.

Test Plan:
Open a file in diffusion, and change the view to "blame", clicking on the line
number should retain the same view.

Reviewed By: epriestley
Reviewers: epriestley, jungejason
CC: aran, epriestley, aizatto
Differential Revision: 344