Fix CID 469129 and 469141 using std::atomic<>

Unlikely, but valid thread-safety concerns by Coverity

src/sbbs3/sbbs.h

@@ -377,6 +377,7 @@ typedef struct js_callback {
 /* Synchronet Node Instance class definition */
 #if defined(__cplusplus) && defined(JAVASCRIPT)
 
+#include <atomic>
 #include <string>
 #include <unordered_map>
 
@@ -414,7 +415,7 @@ public:
 	CRYPT_SESSION	ssh_session=-1;
 #endif
 	int		session_channel=-1;
-	bool	ssh_mode = false;
+	std::atomic<bool> ssh_mode = false;
 	SOCKET	passthru_socket=INVALID_SOCKET;
 	bool	passthru_socket_active = false;
 	void	passthru_socket_activate(bool);
@@ -467,7 +468,7 @@ public:
 	uchar	telnet_cmd[64]{};
 	uint	telnet_cmdlen = 0;
 	uint	telnet_cmds_received = 0;
-	uint	telnet_mode = 0;
+	std::atomic<uint> telnet_mode = 0;
 	/* 	input_thread() writes to these variables: */
 	uchar	telnet_last_rxch = 0;
 	char	telnet_location[128]{};