Fix database notice errors in updated many user experiment, a=chris

diff --git a/tests/ManyUserExperiment.php b/tests/ManyUserExperiment.php
index 7130062e1..5fad12999 100644
--- a/tests/ManyUserExperiment.php
+++ b/tests/ManyUserExperiment.php
@@ -96,7 +96,12 @@ for ($i = 0; $i < C\ME_NUM_GROUPS; $i++) {
 for ($i = 0; $i < C\ME_NUM_GROUPS; $i++) {
     $user_id = $user_ids[$i];
     for ($j = 1; $j < ($i/10)+1; $j++) {
-        $group_model->addUserGroup($user_id, $group_ids[$j], C\ACTIVE_STATUS);
+        if ($j != $i) {//by above user $i is owner (and so in) group $i
+            echo "Adding User $i (user id $user_id) to ".
+                "Group $j (group id {$group_ids[$j]})\n";
+            $group_model->addUserGroup($user_id, $group_ids[$j],
+                C\ACTIVE_STATUS);
+        }
     }
 }
 $impression_model = new M\ImpressionModel();