Fix a bunch more memory leaks in the tests.

doc/HACKING/WritingTests.txt

@@ -329,7 +329,9 @@ into test/slow if it genuinely needs to be run.
 Tests should not alter global state unless they run with TT_FORK: Tests
 should not require other tests to be run before or after them.
 
-Tests should not leak memory or other resources.
+Tests should not leak memory or other resources.  To find out if your tests
+are leaking memory, run them under valgrind (see HelpfulTools.txt for more
+information on how to do that).
 
 When possible, tests should not be over-fit to the implementation.  That is,
 the test should verify that the documented behavior is implemented, but

src/or/rendcache.c

@@ -416,9 +416,10 @@ validate_intro_point_failure(const rend_service_descriptor_t *desc,
       /* This intro point is in our cache, discard it from the descriptor
        * because chances are that it's unusable. */
       SMARTLIST_DEL_CURRENT(desc->intro_nodes, intro);
-      rend_intro_point_free(intro);
       /* Keep it for our new entry. */
       digestmap_set(new_entry->intro_failures, (char *) identity, ent_dup);
+      rend_intro_point_free(intro);
+
       continue;
     }
   } SMARTLIST_FOREACH_END(intro);