Move DS's Kerberos env vars to unit file

The IPA specific env vars KRB5_KTNAME and KRB5CCNAME are now defined in
a instance specific ipa-env.conf unit file.

Fixes: https://pagure.io/freeipa/issue/7860
Signed-off-by: Christian Heimes <cheimes@redhat.com>
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>

install/share/Makefile.am

@@ -39,6 +39,7 @@ dist_app_DATA =				\
 	replica-acis.ldif		\
 	replica-prevent-time-skew.ldif  \
 	ds-nfiles.ldif			\
+	ds-ipa-env.conf.template	\
 	dns.ldif			\
 	dnssec.ldif			\
 	domainlevel.ldif			\

install/share/ds-ipa-env.conf.template

@@ -0,0 +1,5 @@
+# Installed and maintained by ipa update tools, please do not modify
+
+[Service]
+Environment=KRB5_KTNAME=$KRB5_KTNAME
+Environment=KRB5CCNAME=$KRB5CCNAME