[OCIS] ocs v1, normal user can list members in the group

[dpakach]

steps

1. create a normal user and add the user to a group
2. As the user try to list the members of the group

Expected

it should give forbidden

Actual

it is possible to list the members of the group

❯ curl https://localhost:9200/ocs/v1.php/cloud/groups/group1 -u einstein:relativity -k 
<?xml version="1.0" encoding="UTF-8"?>
<ocs><meta><status>ok</status><statuscode>100</statuscode><message>OK</message></meta><data><users><element>einstein</element></users></data></ocs>%