Fix memory leak in threadLocal on implicit transactions (#1711)

* refactor TestExecutionComplete

* Add more tests to discover missing threadScope cleanups

* FIX: clear threadScope on implicit created Jdbc transactions

* FIX: clear threadScope on completed JTA transactions

* Revert "FIX: clear threadScope on completed JTA transactions"

This reverts commit f844405542.

src/main/java/io/ebeaninternal/server/transaction/DefaultTransactionScopeManager.java

@@ -42,5 +42,9 @@ public class DefaultTransactionScopeManager extends TransactionScopeManager {
     DefaultTransactionThreadLocal.set(serverName, trans);
   }
 
+  @Override
+  public void clear(SpiTransaction trans) {
+    DefaultTransactionThreadLocal.clear(serverName, trans);
+  }
 
 }