Description of problem:
Evolution doesn't apply changed time in 'hide completed tasks' setting 
immediately.  If you change the time after task should be hidden, and complete 
some task, it is hidden after old value of time, not the new.
If you reload the task list somehow (e.g. restart Evolution, switch to mail and 
back to tasks, etc), the new settings applies.

Version-Release number of selected component (if applicable):
Evolution 2.8.0

How reproducible:
always

Steps to Reproduce:
1. Create a few tasks and make sure 'Hide completed tasks' is disabled in 
preferences
2. Change settings to be 'Hide completed tasks after 1 minute'
3. Make one task completed
4. Wait one minute. Completed task hides.
5. Change settings to be 'Hide completed tasks after 0 minute'
6. Make other task completed. It hides after 1 minute, but it should hide 
immediately.
  
Actual results:
Changed settings are applied after reloading the task list somehow.

Expected results:
Changed settings are applied by closing settings dialog.

Additional info: