Put focus on the password recovery flash (a11y)
Put focus on the password recovery flash (a11y)

Refs USERS-450
Refs UXS-50

Accessibility audit pointed out that after the password reset
instructions are issued, focus should be on the alert that just
got put up, not back on the email input field.

Test plan:
* At the Canvas login page, click on "Forgot Password?"
* Enter an email address and click on "Request Password"
* Flash message should come up about the reset message being
  sent
* Focus should be on the close X button of that flash message

Change-Id: I1dd5eb5e94378e1ffd782f2ce16694baed677783
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/231464
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
QA-Review: Pierce Arner <de38b793164d9bfa12fc4185260c174139808169@instructure.com>
Reviewed-by: Keith Garner <a1a80143a840c140f31c3495ebbd9ec906e09fed@instructure.com>
Reviewed-by: Laura Gonzalez-Horwitz <7fd1adc466f6c2902e6930f85ab8510191346c59@instructure.com>
Product-Review: Jonathan Fenton <5549b92428699b688d6c4f80786628c27e48a3e1@instructure.com>

sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms