Ticket 49448 - dynamic default pw scheme based on environment.
Bug Description: In some cases the hardcoded default pw scheme
is not available, IE FIPS mode doesn't support pbkdf2. In this
case we need to support returning an appropriate scheme based
on environment.
Fix Description: Add a new scheme name called "DEFAULT" with
a mechanic that pw_name2scheme will use this with environment
information to return an appropriate scheme.
https://pagure.io/389-ds-base/issue/49448
Author: wibrown
Review by: mreynolds, spichugi (Thanks!)