Update password storage scheme references in the server so that they use DNs
rather than storage scheme names.  This will allow better consistency in the
configuration, since all other references between configuration objects are
DN-based, and it will work better with the upcoming aggregation support.
It also eliminates the need to know the storage scheme name, which is not
obvious from looking at the configuration entry for the storage scheme, and
can actually vary in some implementations depending on whether it's used with a
user password or auth password syntax attribute.

OpenDS Issue Number:  2155