SERVER-37837 Get rid of TransactionReaper (Part 1)

This change gets rid of the TransactionReaper's usage of the
ReplicationCoordinator for checking whether it is primary or not and
makes the LogicalSessionCache joinable on shutdown.

It also removes the TransactionReaper's grouping per-shard optimization
and moves it all under SessionCollectionSharded.

1 files changed, 5 insertions, 1 deletions

diff --git a/src/mongo/db/logical_session_cache_test.cpp b/src/mongo/db/logical_session_cache_test.cpp
index e7b61b664b0..a5cc6e8eed0 100644
--- a/src/mongo/db/logical_session_cache_test.cpp
+++ b/src/mongo/db/logical_session_cache_test.cpp
@@ -79,7 +79,11 @@ public:
         auto mockService = stdx::make_unique<MockServiceLiaison>(_service);
         auto mockSessions = stdx::make_unique<MockSessionsCollection>(_sessions);
         _cache = stdx::make_unique<LogicalSessionCacheImpl>(
-            std::move(mockService), std::move(mockSessions), nullptr /* reaper */);
+            std::move(mockService),
+            std::move(mockSessions),
+            [](OperationContext*, SessionsCollection&, Date_t) {
+                return 0; /* No op*/
+            });
     }
 
     void waitUntilRefreshScheduled() {