Generation of CSRF token is too expensive

When disabling the country filter, response time gets noticeably slower. This can be reproduced in our demo but not in a local installation with the bundle. 

Steps to reproduce:

• Execute the following command in order to measure the response time:

  curl -so /dev/null -w '%{time_starttransfer} Seconds \n' https://demopublic.magnolia-cms.com

• Add configuration property /server/filters/country@enabled with value false in order to disable the filter and execute same command than in step 1.

Expected result: response time is similar or even lower as filter execution is avoided.
Actual result: response time is noticeably higher:

$ curl -so /dev/null -w '%{time_starttransfer} Seconds \n' https://demopublic.magnolia-cms.com/travel 
0.998357 Seconds 

COUNTRY FILTER IS DISABLED

$ curl -so /dev/null -w '%{time_starttransfer} Seconds \n' https://demopublic.magnolia-cms.com/travel 
2.363181 Seconds 

Timebox for investigation: 3 SP

• Verify findings, can they be used as a solution?
• Consider potential implications (login page CSRF)