For policy attach/detach API to work correctly the server should hold a
lock before reading existing policy mapping and until after writing the
updated policy mapping. This is fixed in this change.
A site replication bug, where LDAP policy attach/detach were not
correctly propagated is also fixed in this change.
Bonus: Additionally, the server responds with the actual (or net)
changes performed in the attach/detach API call. For e.g. if a user
already has policy A applied, and a call to attach policies A and B is
performed, the server will respond that B was attached successfully.