torture: Add sftp session pointer to torture_state

Signed-off-by: Andreas Schneider <asn@cryptomilk.org>

tests/torture.h

@@ -73,6 +73,7 @@ struct torture_state {
     char *srv_config;
     struct {
         ssh_session session;
+        struct torture_sftp *tsftp;
     } ssh;
 };