Fix bugs with custom url pattern matching for EndToEnd test.

This CL both gets rid of 3 extra variables (cleaning up a TODO) and also
allows this test to be run against trybots and non-canary builders.

Unlike canary builders, trybot's and other builders do not follow a
${board}-release pattern. Instead they can be pretty much

<anything>/<version>. The devserver deals with this by just using the
archive_url (which embeds the build) to find/store the payload. We leverage
this and only use image to base our url's.

Note this also allows us to run AU Test on paladin's and chrome pfq's.

BUG=chromium:217855
TEST=Pylint + unittests + local autotest setup with endToEnd test.

Change-Id: I765d90bfabb4933e35b3de914f82b817c05982cb
Reviewed-on: https://gerrit.chromium.org/gerrit/45759
Commit-Queue: Chris Sosa <sosa@chromium.org>
Reviewed-by: Chris Sosa <sosa@chromium.org>
Tested-by: Chris Sosa <sosa@chromium.org>
3 files changed