Fix property access on concatenation-map (#159)
Fix property access on concatenation-map (#159)

In PHP you cannot dereference array-keys via `->`, so each field from
`concatenationmap` was empty because of `$userAttributes->$item`.
privacyidea/simplesamlphp-module-privacyidea,privacyidea/simplesamlphp-module-privacyidea