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>

ipaplatform/base/paths.py

@@ -382,6 +382,8 @@ class BasePathNamespace:
     VAR_LOG_DIRSRV_INSTANCE_TEMPLATE = "/var/log/dirsrv/slapd-%s"
     SLAPD_INSTANCE_ACCESS_LOG_TEMPLATE = "/var/log/dirsrv/slapd-%s/access"
     SLAPD_INSTANCE_ERROR_LOG_TEMPLATE = "/var/log/dirsrv/slapd-%s/errors"
+    SLAPD_INSTANCE_SYSTEMD_IPA_ENV_TEMPLATE = \
+        "/etc/systemd/system/dirsrv@%s.service.d/ipa-env.conf"
     # Legacy 389 commands
     LDIF2DB = '/usr/sbin/ldif2db'
     DB2LDIF = '/usr/sbin/db2ldif'