SS/USSD: fix: properly (re)schedule NCSS session timeout

It may happen that either the MS or an ESME would become
unresponsive, e.g. due to a bug, or a dropped message. This
is why we have SS session timeout, that prevents keeping
'stalled' sessions forever.

For some reason, it wasn't properly resceduled in case of
subsequent SS/USSD activity, so the lifetime of a session
was limited. Let's properly (re)schedule it.

Change-Id: I11aeacf012b06d3d0b5cc6e64baecf857b645fda
Related: OS#3717
1 file changed