[autotest] Pipe suite_name through client devserver code.

To reduce the overhead involved with fetching control files
from the devserver we generate a mapping of suite->control
files at build time. This cl will ask the control file getter
to fetch the control files for a given suite instead of all
the control files associated with an image.

Also removing SUITE = None from some networking test control
files, and patched unittests.

BUG=chromium:252398
TEST=Ran a suite with many control files. Made sure the suite->
     control file mapping falls back to the old code when a bad suite
     name is specified. Compared the test objects created in the old
     version vs those created with this change.
     Ran unittests.

CQ-DEPEND=CL:I6b590c8c40a863e6744875a26ac228ffd4dd8794

Change-Id: I4274c78764ffaaabef1ed48cdb40f523e307938d
Reviewed-on: https://gerrit.chromium.org/gerrit/63182
Tested-by: Prashanth Balasubramanian <beeps@chromium.org>
Reviewed-by: Dan Shi <dshi@chromium.org>
Commit-Queue: Prashanth Balasubramanian <beeps@chromium.org>
9 files changed