(bug 44822) add verbosity if user tries to add already assigned OpenID

When user tried to add an OpenID which is already assigned to their account
or to another user's account, then the error text shows this conflicting OpenID
as actually given and  sent by the OpenID Provider.

Two message texts have changed their name and added a parameter $1 (the conflicting
OpenID).

Change-Id: I7d7b389a495c62b14656823e8976a3bbb32c9c37