P2PServer: ban peers that disconnect without finishing handshake

src/p2p_server.h

@@ -63,6 +63,7 @@ public:
 		void reset() override;
 		bool on_connect() override;
 		bool on_read(char* data, uint32_t size) override;
+		void on_read_failed(int err) override;
 
 		// Both peers send handshake challenge immediately after a connection is established
 		// Both peers must have the same consensus ID for handshake to succeed