Fix recovery bug (transaction ID bumping)

Summary:
When performing recovery, ensure that the transaction ID in engine is
bumped to one after the max tx id seen in recovery.

Reviewers: dgleich

Reviewed By: dgleich

Subscribers: pullbot

Differential Revision: https://phabricator.memgraph.io/D1312

tests/unit/transaction_engine_single_node.cpp

@@ -74,3 +74,10 @@ TEST(Engine, RunningTransaction) {
   EXPECT_NE(t1, engine.RunningTransaction(t0->id_));
   EXPECT_EQ(t1, engine.RunningTransaction(t1->id_));
 }
+
+TEST(Engine, EnsureTxIdGreater) {
+  SingleNodeEngine engine;
+  ASSERT_LE(engine.Begin()->id_, 40);
+  engine.EnsureNextIdGreater(42);
+  EXPECT_EQ(engine.Begin()->id_, 43);
+}