Bug 829213 - unhashed#user#password visible after changing password
Bug Description: unhashed password is stored in the entry in memory
when an entry/a password is added or the password is modified.
The password could be visible by the ordinary search if the type
"unhashed#user#password" is specified in the attribute list.
1. Set "unhashed#user#password" to the forbidden attribute list,
which is dropped from the search attribute list.
2. Get effective right does not return "unhashed#user#password"
3. In the modify operation, adding "unhashed#user#password" to or
deleting "unhashed#user#password" from the entry never returns
an error regardless of the attribute value. Internally, the
operation is ignored.