Currently is_admin flag is always False. As a result
some of the admin operations are not working.
For example, quotas-list is not listing all the
user quotas.
This change sets the flag correctly based on the
roles assigned to the user and policies defined
in policy.json.
Change-Id: I01534ccf1cf1e635282db497e0e026bea19c3bd2
Closes-Bug: #1660843