Fix tests NH 3848 for Firebird

Author: Iwanow, Mihail (EXT)

src/NHibernate.Test/NHSpecificTest/NH3848/TestFixture.cs

@@ -398,7 +398,15 @@ public virtual void ChildCollectionsFromLeftOuterJoinOnlyWithRestrictionShouldNo
 			using (var session = OpenSession())
 			using (IDbCommand cmd = session.Connection.CreateCommand())
 			{
-				cmd.CommandText = "DELETE FROM Orders; DELETE FROM Companies;";
+				cmd.CommandText = "DELETE FROM Orders;";
+				cmd.ExecuteNonQuery();
+				cmd.Connection.Close();
+			}
+
+			using (var session = OpenSession())
+			using (IDbCommand cmd = session.Connection.CreateCommand())
+			{
+				cmd.CommandText = "DELETE FROM Companies;";
 				cmd.ExecuteNonQuery();
 				cmd.Connection.Close();
 			}