Set telnets_active to false on error, not true.

This way, when an error occurs, it will at least terminate the
session instead of requiring you to disconnect yourself.

This partially addresses issue 174, assuming it's actually telnets.

src/syncterm/telnets.c

@@ -42,12 +42,15 @@ telnets_input_thread(void *args)
 			continue;
 		if (cryptStatusError(status)) {
 			if ((status == CRYPT_ERROR_COMPLETE) || (status == CRYPT_ERROR_READ)) { /* connection closed */
-
-				telnets_active = true;
+				pthread_mutex_lock(&telnets_mutex);
+				telnets_active = false;
+				pthread_mutex_unlock(&telnets_mutex);
 				break;
 			}
 			cryptlib_error_message(status, "recieving data");
-			telnets_active = true;
+			pthread_mutex_lock(&telnets_mutex);
+			telnets_active = false;
+			pthread_mutex_unlock(&telnets_mutex);
 			break;
 		}
 		else {
@@ -84,11 +87,15 @@ telnets_output_thread(void *args)
 				pthread_mutex_unlock(&telnets_mutex);
 				if (cryptStatusError(status)) {
 					if (status == CRYPT_ERROR_COMPLETE) { /* connection closed */
-						telnets_active = true;
+						pthread_mutex_lock(&telnets_mutex);
+						telnets_active = false;
+						pthread_mutex_unlock(&telnets_mutex);
 						break;
 					}
 					cryptlib_error_message(status, "sending data");
-					telnets_active = true;
+					pthread_mutex_lock(&telnets_mutex);
+					telnets_active = false;
+					pthread_mutex_unlock(&telnets_mutex);
 					break;
 				}
 				sent += ret;