table: ensure NameTree::lookup(tableEntry) does not return nullptr

NameTree::lookup(tableEntry) is always equivalent to NameTree::lookup(Name).
NameTree::getEntry(tableEntry) should be used when inserting new name tree entry is undesired.

refs #3687

Change-Id: I0b17cd07dde83341976cfe66c85855dfb2fa6e89
diff --git a/daemon/table/measurements.hpp b/daemon/table/measurements.hpp
index 6942124..dd593f6 100644
--- a/daemon/table/measurements.hpp
+++ b/daemon/table/measurements.hpp
@@ -136,7 +136,7 @@
   Entry&
   get(name_tree::Entry& nte);
 
-  /** \tparam K Name or name_tree::Entry
+  /** \tparam K a parameter acceptable by NameTree::findLongestPrefixMatch
    */
   template<typename K>
   Entry*