Users logged out of PMM after some period

User impact: User have to log in to PMM from time to time.

STR:

1. Install PMM 2.11.1 server
2. Open Chrome and log in to PMM with admin/admin credentials
   Given result: User logged out in a few minutes.
   Expected result: User don't logged out until he click on logout link.

PMM server logs are attached.

Original report: Starting with PMM 2.9.0 there have been several reports of users getting logged out after some period (seemingly 5-15 minutes).  Not sure what the exact steps to reproduce are but it's clearly happening more often to users at various places. 

Some examples:

https://forums.percona.com/discussion/55896/pmm2-dashborad-session-timeout#latest

PZ mentioned he sees it when going to InnoDB Details and sitting for 15 minutes or so.  

I've had it happen to me as well but short of just sitting on a page for 10 minutes I'm not sure what the trigger is.