table: make name_tree::Node the sole owner of name_tree::Entry

This commit also improves name_tree::Entry test coverage.

refs #3687

Change-Id: I92375f29fbebab82c67da7dff2ea7a2952ba2cca
diff --git a/daemon/table/name-tree.hpp b/daemon/table/name-tree.hpp
index 8542873..0c24654 100644
--- a/daemon/table/name-tree.hpp
+++ b/daemon/table/name-tree.hpp
@@ -65,7 +65,7 @@
   Entry*
   getEntry(const ENTRY& tableEntry) const
   {
-    return tableEntry.m_nameTreeEntry.lock().get();
+    return Entry::get(tableEntry);
   }
 
 public: // mutation