Network Config: Improve certificate UI

This CL:
* Disables non hardware backed user certs
* Displays an error message when no user certs or no hardware backed
  certs are available
* Fixes edge cases where certifiates are added or removed while the
  config UI is visible
* Adds/improves configuration event logging

Bug: 810079
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I9f2374d16bf2300fd2937c8ce873d40cf4c44321
Reviewed-on: https://chromium-review.googlesource.com/949442
Reviewed-by: Toni Barzic <tbarzic@chromium.org>
Commit-Queue: Steven Bennetts <stevenjb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#541018}
4 files changed