MDL-69102 badge: Fixes broken WHERE clause

When buildilng the 'WHERE' clause, the SQL generated
a query that selected any user who was a member of the
**last** group, not all of the groups.

I believe the query has to be re-worked so that it only
returns users who are in ALL of the groups. This can
be done by a GROUP BY and HAVING.

badges/criteria/award_criteria_cohort.php

@@ -240,13 +240,23 @@ class award_criteria_cohort extends award_criteria {
             return array($join, $where, $params);
         } else {
             // User is a member of ALL of the specified cohorts.
-            $join = " LEFT JOIN {cohort_members} cm ON cm.userid = u.id";
+            $join = ' LEFT JOIN {cohort_members} cm ON cm.userid = u.id';
+            $where = ' AND (';
             $i = 0;
             foreach ($this->params as $param) {
-                $i++;
-                $where = ' AND cm.cohortid = :cohortid'.$i;
+                if ($i == 0) {
+                    $where .= 'cm.cohortid = :cohortid'.$i;
+                } else {
+                    $where .= ' OR cm.cohortid = :cohortid'.$i;
+                }
                 $params['cohortid'.$i] = $param['cohort'];
+                $i++;
             }
+            $where .= ')
+                GROUP BY u.id, bi.badgeid
+                HAVING COUNT(cm.cohortid) = :cohortcount';
+            $params['cohortcount'] = $i;
+
             return array($join, $where, $params);
         }
     }