Enable HWTest phase for all R34 canaries that might need it.

As of a recent change, it is now safe to request HWTest for boards
that don't exist.  This is done so that builders can request HWTest
without regard to whether hardware is available, so that the
builders don't have to track the inventory in the lab.

This change adds a HWTest phase to all canaries that are expected
to eventually need testing for R34, regardless of whether hardware
currently exists in the lab.

BUG=chromium:353541
TEST=python cbuildbot_config_unittest.py

Change-Id: Ia5b8d76b186449c975a2187d089f9c4893d36499
Reviewed-on: https://chromium-review.googlesource.com/196612
Tested-by: Richard Barnette <jrbarnette@chromium.org>
Reviewed-by: Yu-Ju Hong <yjhong@chromium.org>
Reviewed-by: Prashanth B <beeps@chromium.org>
Commit-Queue: Richard Barnette <jrbarnette@chromium.org>
diff --git a/buildbot/cbuildbot_config.py b/buildbot/cbuildbot_config.py
index fe912a9..ef507a8 100755
--- a/buildbot/cbuildbot_config.py
+++ b/buildbot/cbuildbot_config.py
@@ -1844,12 +1844,10 @@
 
 _release.add_config('enguarde-release',
   boards=['enguarde'],
-  hw_tests=[],
 )
 
 _release.add_config('expresso-release',
   boards=['expresso'],
-  hw_tests=[],
 )
 
 _release.add_config('falco-release',
@@ -1951,7 +1949,6 @@
 _release.add_config('quawks-release',
   incompatible_instruction_set,
   boards=['quawks'],
-  hw_tests=[],
 )
 
 _release.add_config('stout-release',