Modify user_in_hubmap_read_group to utilize commons has_read_privs method

[maxsibilla]

Modify method to be:

    if 'Authorization' not in request.headers:
        return False

    try:
        user_token = get_user_token(request)
        read_privs = auth_helper_instance.has_read_privs(user_token)
        if isinstance(read_privs, Response):
            msg = read_privs.get_data().decode()
            logger.exception(msg)
            return False            

    except Exception as e:
        # Log the full stack trace, prepend a line with our message
        logger.exception(e)

        # If the token is not a groups token, no group information available
        # The commons.sn_auth.AuthCache would return a Response with 500 error message
        # We treat such cases as the user not in the SenNet-READ group
        return False

    return read_privs

[maxsibilla]

After discussing this card (hubmapconsortium/commons#119) with @shirey the simple solution is to re-use this commons method for consistency sake.