Session expired even if user still active during editing content.

Scenario reproduced in HAP project in channel manager:

1. In /hippo:configuration/hippo:frontend/cms/cms-static/root set max.inactive.interval.minutes to 1 minute.
2. Login, go to Channel Manager.
3. During one minute try to manipulate with editing content: open right side panel and try edit some fields. Do not  open right side panel for another document during that minute. Note that request are fired e.g. auto-draft requests to save values of the fields. 

Problem: In one minute user automatically logged out.

Expected: No logout for active user.