With the recent encryption of the HTTPD keys, it's also necessary
to count with this scenario during upgrade and create the password
for the HTTPD private key along the cert/key pair.
This commit also moves the HTTPD_PASSWD_FILE_FMT from ipalib.constants
to ipaplatform.paths as it proved to be too hard to be used that way.
https://pagure.io/freeipa/issue/7421
Reviewed-By: Christian Heimes <cheimes@redhat.com>