Revert of Enable strict coverage for step module

recipes/example/defer.py

+# Copyright 2014 The LUCI Authors. All rights reserved.
+# Use of this source code is governed under the Apache License, Version 2.0
+# that can be found in the LICENSE file.
+
+DEPS = [
+  'step',
+]
+
+def RunSteps(api):
+  ran_both = False
+  try:
+    with api.step.defer_results():
+      api.step("testa", ["echo", "testa"])
+      api.step("testb", ["echo", "testb"])
+      ran_both = True
+  finally:
+    assert ran_both
+
+
+def GenTests(api):
+  yield api.test('basic')
+
+  yield (
+      api.test('one_fail') +
+      api.step_data('testa', retcode=1)
+    )