Ensuring absence of members (services and targets) that do not exist may
not fail as they are not members for servicedelegationtarget and
servicedelegationrule.

servicedelegation_normalize_principals in ansible_freeipa_module has
been extended with a check_exists argument that defaults to False. state
== "present" is now given as this argument to turn on the element exists
check only if elements should be added.