R1:774211af7657

Tweak style on "Create Another Task" button

Summary:
Not totally sure I'm in love with this but I think it's somewhat non-terrible,
despite the lack of lens flare.

Also made "Cancel" take you back to the task if you got to "Create" from "Create
Another Task".

Test Plan:
- Style:
https://secure.phabricator.com/file/view/PHID-FILE-ad37d3c1f3b2c7a7a7d1/
- Hit "Cancel" from "Create Another", got sent back to task.
- Hit "Cancel" from normal create, got sent back to list.
- Tried to save an invalid…