Manage Groups search ignores filters

This is a defect in 4.7.7 that didn't affect 4.7.6. It is reproducible in the Drupal & demo.

1. Visit the Manage Groups page. See a paginated list of all groups
2. Enter a filter value and move focus off the filter field to force an AJAX refresh. Expect to see paginated list of groups filtered by the criterion, but all groups are included in results.

It appears to be a regression added by https://github.com/civicrm/civicrm-core/pull/8265 and in particular the change to CRM/Group/Page/AJAX.php in https://github.com/civicrm/civicrm-core/pull/8265/commits/9c3f979fa4a51aaae9b7347c8bbe156cf483eab5

The offending lines are 53 to 56 in CRM/Group/Page/AJAX.php ...

53 $params = CRM_Core_Page_AJAX::defaultSortAndPagerParams();
54
55 // get group list
56 $groups = CRM_Contact_BAO_Group::getGroupListSelector($params);

Line 53 replaces the passed-in parameters with default ones every time, so all groups are returned.