Change ray.worker.cleanup -> ray.shutdown and improve API documentation. (#2374)

* Change ray.worker.cleanup -> ray.shutdown and improve API documentation.

* Deprecate ray.worker.cleanup() gracefully.

* Fix linting

python/ray/tune/test/trial_runner_test.py

@@ -26,7 +26,7 @@ class TrainableFunctionApiTest(unittest.TestCase):
         ray.init(num_cpus=4, num_gpus=0)
 
     def tearDown(self):
-        ray.worker.cleanup()
+        ray.shutdown()
         _register_all()  # re-register the evicted objects
 
     def testPinObject(self):
@@ -366,7 +366,7 @@ class RunExperimentTest(unittest.TestCase):
         ray.init()
 
     def tearDown(self):
-        ray.worker.cleanup()
+        ray.shutdown()
         _register_all()  # re-register the evicted objects
 
     def testDict(self):
@@ -441,7 +441,7 @@ class VariantGeneratorTest(unittest.TestCase):
         ray.init()
 
     def tearDown(self):
-        ray.worker.cleanup()
+        ray.shutdown()
         _register_all()  # re-register the evicted objects
 
     def testParseToTrials(self):
@@ -575,7 +575,7 @@ class VariantGeneratorTest(unittest.TestCase):
 
 class TrialRunnerTest(unittest.TestCase):
     def tearDown(self):
-        ray.worker.cleanup()
+        ray.shutdown()
         _register_all()  # re-register the evicted objects
 
     def testTrialStatus(self):

python/ray/tune/test/trial_scheduler_test.py

@@ -29,7 +29,7 @@ class EarlyStoppingSuite(unittest.TestCase):
         ray.init()
 
     def tearDown(self):
-        ray.worker.cleanup()
+        ray.shutdown()
         _register_all()  # re-register the evicted objects
 
     def basicSetup(self, rule):
@@ -196,7 +196,7 @@ class HyperbandSuite(unittest.TestCase):
         ray.init()
 
     def tearDown(self):
-        ray.worker.cleanup()
+        ray.shutdown()
         _register_all()  # re-register the evicted objects
 
     def schedulerSetup(self, num_trials):
@@ -561,7 +561,7 @@ class PopulationBasedTestingSuite(unittest.TestCase):
         ray.init()
 
     def tearDown(self):
-        ray.worker.cleanup()
+        ray.shutdown()
         _register_all()  # re-register the evicted objects
 
     def basicSetup(self, resample_prob=0.0, explore=None):
@@ -781,7 +781,7 @@ class AsyncHyperBandSuite(unittest.TestCase):
         ray.init()
 
     def tearDown(self):
-        ray.worker.cleanup()
+        ray.shutdown()
         _register_all()  # re-register the evicted objects
 
     def basicSetup(self, scheduler):

python/ray/tune/test/tune_server_test.py

@@ -51,7 +51,7 @@ class TuneServerSuite(unittest.TestCase):
             self.runner = None
         except Exception as e:
             print(e)
-        ray.worker.cleanup()
+        ray.shutdown()
         _register_all()
 
     def testAddTrial(self):