quickfix

Fix generation of session id for ruby 2.0

W/o this change a test which uses mixin of session addressing like:

E1,8=....
...
E8=

would fail when modern version of ruby is used.

At this moment there are no such tests in master. Last of them were
fixed under 9e8a815cd3ec0546ca3a2bbd26f6683fdfa4eb20