bootstrap_daemon: fix missing virtual destructor and lambda capture (clang warning)

src/rpc/bootstrap_node_selector.h

@@ -54,6 +54,8 @@ namespace bootstrap_node
 
   struct selector
   {
+    virtual ~selector() = default;
+
     virtual void handle_result(const std::string &address, bool success) = 0;
     virtual boost::optional<node_info> next_node() = 0;
   };

src/rpc/core_rpc_server.cpp

@@ -224,7 +224,7 @@ namespace cryptonote
     }
     else if (address == "auto")
     {
-      auto get_nodes = [this, credits_per_hash_threshold]() {
+      auto get_nodes = [this]() {
         return get_public_nodes(credits_per_hash_threshold);
       };
       m_bootstrap_daemon.reset(new bootstrap_daemon(std::move(get_nodes), rpc_payment_enabled));