Fixed SST timer being reset to the lowest value on session refresh.
Removed useless SST timer reset.

It could potentially reset the dialog lifetime to its max value when it
is not required.
Merge pull request #23 from dsandras/ds-sst-morefixes

Fixed SST timer being reset to the lowest value on session refresh.
Credits go to Damien Sandras from Be IP s.a. @ http://www.beip.be