Update client: add support for running actions.

The code is work in progress for the improved recovery component.
Nothing is actually run at the moment but there is
sufficient code for review.

Next step is to build a command runner which runs the payload.

Bug: 687231
Change-Id: Ie0ae46e7f5f7dd7f5c8ccfd530d707373891af15
Reviewed-on: https://chromium-review.googlesource.com/536294
Commit-Queue: Sorin Jianu <[email protected]>
Reviewed-by: Joshua Pawlicki <[email protected]>
Reviewed-by: Tommy Li <[email protected]>
Cr-Commit-Position: refs/heads/master@{#479817}
12 files changed