run_tests: delete old wrapper tool

Now that we only have python3 to worry about, delete the old logic
and rename run_pytest to the canonical run_tests location.  The
diff looks bad, but that's because we're deleting run_tests and
then renaming run_pytest on top of it.

BUG=chromium:997354
TEST=`./run_tests` passes

Change-Id: I7c43a3b671e0c5be531cef760259d18ee41167b9
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/2822082
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Chris McDonald <cjmcdonald@chromium.org>
diff --git a/api/controller/test.py b/api/controller/test.py
index 372a50e..168cb81 100644
--- a/api/controller/test.py
+++ b/api/controller/test.py
@@ -147,11 +147,7 @@
 @validate.validation_complete
 def ChromiteUnitTest(_input_proto, _output_proto, _config):
   """Run the chromite unit tests."""
-  cmd = [os.path.join(constants.CHROMITE_DIR, 'scripts', 'run_tests')]
-  # TODO(vapier): Delete this stub.
-  cmd = ['true']
-  result = cros_build_lib.run(cmd, check=False)
-  if result.returncode == 0:
+  if test.ChromiteUnitTest():
     return controller.RETURN_CODE_SUCCESS
   else:
     return controller.RETURN_CODE_COMPLETED_UNSUCCESSFULLY
@@ -162,10 +158,8 @@
 @validate.validation_complete
 def ChromitePytest(_input_proto, _output_proto, _config):
   """Run the chromite unit tests."""
-  if test.ChromitePytest():
-    return controller.RETURN_CODE_SUCCESS
-  else:
-    return controller.RETURN_CODE_COMPLETED_UNSUCCESSFULLY
+  # TODO(vapier): Delete this stub.
+  return controller.RETURN_CODE_SUCCESS
 
 
 @faux.all_empty