This function will be used in servicedelegation target and rule modules
to normalize principals given in the tasks. These can be service and host
principals and also aliases.

Note: The use of host principals requires IPA 4.9.0 or later. fail_json
is called if the version is lower.

servicedelegation_normalize_principals contains two embedded fuctions.
One is normalize_principal_name that has been copied from
ipaserver/plugins/servicedelegation.py, the other is the generic
function _check_exists to be able to check if a host or service exists.