CaloTPCnv: Adjust use of DataPool to work properly with locking.

Upcoming changes to DataPool will have the DataPool object take out a lock.
This is needed for proper MT operation, but means that creating two
instances with the same type in the same thread will deadlock.
This wouldn't usually happen, but it did occur in one of the unit tests.

Calorimeter/CaloCnv/CaloTPCnv/test/CaloClusterContainerCnv_test.cxx

@@ -392,7 +392,13 @@ int main()
   // These allocate static data in ctors.
   ElementLinkCnv_p2<ElementLink<CaloShowerContainer> >  dumcnv1;
   ElementLinkCnv_p2<ElementLink<CaloCellLinkContainer> >  dumcnv2;
-  DataPool<CaloCluster> pooldum;
+  {
+    // Need to instantiate an instance of this before Leakcheck,
+    // to get the allocator created.  But the instance will also
+    // hold a lock on the allocator, so can't leave this live
+    // or we'll deadlock.
+    DataPool<CaloCluster> pooldum;
+  }
   Athena_test::Leakcheck check;
   std::unique_ptr<const CaloClusterContainer> clust = make_clusters();
   testit<CaloClusterContainer_p7, CaloClusterContainerCnvTest_p7> (*clust, 7);