Replace ipalib with ipa command line
Ipsilion uses ipalib just to parse FreeIPA's config file and to create a
service principal. This can be easily archived by shelling out to the
ipa command line tool. The server, realm, and domain names are not
required either.
* Use subprocess.check_output()
* ipa-getkeytab no longer needs '-s server' argument. It can parse
/etc/ipa/default.conf on its own.
* The service principal name doesn't need the @REALM suffix. FreeIPA
adds it automatically.
The change is necessary, because FreeIPA 4.8 will drop support for
Python 2 and Ipsilon is still not fully ported to Python 3.
See: https://fedoraproject.org/wiki/Changes/FreeIPA_Python_2_Removal
Signed-off-by: Christian Heimes <cheimes@redhat.com>