[master] use reverse_iterator instead of const_reverse_iterator in a for loop.

this is a workaround for build problem for the solaris buildbot (both g++ and
sunstudio); they don't seem to work well with the const iterator in operator!=.

src/bin/auth/tests/query_unittest.cc

@@ -341,7 +341,9 @@ MockZoneFinder::find(const Name& name, const RRType& type,
         }
 
         // Normal case
-        for (Domains::const_reverse_iterator it = domains_.rbegin();
+        // XXX: some older g++ complains about operator!= if we use
+        // const_reverse_iterator
+        for (Domains::reverse_iterator it = domains_.rbegin();
              it != domains_.rend();
              ++it) {
             RRsetStore::const_iterator nsec_it;