This commit provides additional functionality that is logically relat…

…ed to the

earlier commit 41b9a6e

Original commit message:

#384 Rename ApplyAsync to ApplyOperation and get rid of the unused apply thread pool

Summary:
To paraphrase @lorinlee on #384: The function name
OperationDriver::ApplyAsync is confusing, and the comments of this function is outdated. It says
that "ApplyAsync() submits ApplyTask() to the apply_pool_", but in fact it is not true. The
invocation of this function is synchronous. Also, apply_pool_ in OperationDriver and even TabletPeer
should be removed because they are not being used.

Test Plan: Jenkins

Reviewers: sergei, bogdan, hector

Reviewed By: hector

Subscribers: bharat, kannan, ybase

Differential Revision: https://phabricator.dev.yugabyte.com/D5292

ent/src/yb/tablet/tablet_peer.h

@@ -13,9 +13,9 @@ class TabletPeer : public yb::tablet::TabletPeer{
   typedef yb::tablet::TabletPeer super;
  public:
   TabletPeer(const scoped_refptr<TabletMetadata>& meta,
-             const consensus::RaftPeerPB& local_peer_pb, ThreadPool* apply_pool,
+             const consensus::RaftPeerPB& local_peer_pb,
              Callback<void(std::shared_ptr<StateChangeContext> context)> mark_dirty_clbk)
-      : super(meta, local_peer_pb, apply_pool, mark_dirty_clbk) {}
+      : super(meta, local_peer_pb, mark_dirty_clbk) {}
 
  protected:
   std::unique_ptr<Operation> CreateOperation(consensus::ReplicateMsg* replicate_msg) override;