network: establish sessions without spending withheld request attempts

src/node_cache.cpp

@@ -9,6 +9,12 @@ constexpr size_t CLEANUP_MAX_NODES {4 * 1024};
 constexpr size_t CLEANUP_FREQ {4 * 1024};
 
 NodeCache::~NodeCache()
+{
+    clear();
+}
+
+void
+NodeCache::clear()
 {
     cache_4.setExpired();
     cache_6.setExpired();