Fix returning to a smart group search after adding an activity.

The previous fix for this did not include the civicrm/group/search url
in the list of possible urls to return to; thus smart groups were still
broken for this workflow.

Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
Merge pull request #4124 from tohojo/adv-search-fix

Fix returning to a smart group search after adding an activity.