Add test for releasing connections back to the server

src/connection_registry.hpp

@@ -63,7 +63,10 @@ public:
   ConnectionRegistry &operator=(ConnectionRegistry &&) = delete;
 
 private:
-  Connection **connections_; ///< mmap'd array of raw connection pointers
-  size_t max_fds_;           ///< Maximum file descriptor limit
-  size_t aligned_size_;      ///< Page-aligned size for munmap
+  std::atomic<Connection *>
+      *connections_;    ///< mmap'd array of raw connection pointers. It's
+                        ///< thread-safe without since epoll_ctl happens before
+                        ///< epoll_wait, but this makes tsan happy /shrug.
+  size_t max_fds_;      ///< Maximum file descriptor limit
+  size_t aligned_size_; ///< Page-aligned size for munmap
 };