The withdrawal call-to-action and withdrawal transaction details dialog
showed different fees, as the "overhead" for unwithdrawable amounts in a
reserve was not included in the withdrawal CTA.
The withdrawal CTA now shows the same fees as the transaction details.
We now always increment the next retry timeout before doing anything
else, so that it is impossible to accidentally retry immediately.
This fixes a bug where we previously made many, very frequent requests
to the bank integration API.