CAless installation: set the perms on KDC cert file
In CA less installation, the KDC certificate file does not have
the expected 644 permissions. As a consequence, WebUI login
fails.
The fix makes sure that the KDC cert file is saved with 644 perms.
Fixes: https://pagure.io/freeipa/issue/8440
Reviewed-By: Rob Crittenden <rcritten@redhat.com>