Add option to evict keys LRU from the sharded redis tables (#3499)

* wip

* wip

* format

* wip

* note

* lint

* fix

* flag

* typo

* raise timeout

* fix

* optional get

* fix flag

* increase timeout in test

* update docs

* format

python/ray/profiling.py

@@ -128,6 +128,19 @@ class Profiler(object):
             self.events.append(event)
 
 
+class NoopProfiler(object):
+    """A no-op profile used when collect_profile_data=False."""
+
+    def start_flush_thread(self):
+        pass
+
+    def flush_profile_data(self):
+        pass
+
+    def add_event(self, event):
+        pass
+
+
 class RayLogSpanRaylet(object):
     """An object used to enable logging a span of events with a with statement.