Fix secrets portal wallet access
The current code checks whether the wallet is open and only if it's not calls openAsync
However kwallet internally tracks which apps have openend the wallet and only gives access to those that have called open
This works fine if the portal request triggered the opening of the wallet and subsequent access works, but if the wallet was opened by another app before any attempt to read from the wallet will fail
To fix this always open the wallet before accessing. This allows to simplify the code since we then can tie a portal request to a KWallet transaction ID.
Also consistently use xdg-desktop-portal as appid when making calls to kwallet