Make sure we use a valid price table when funding an account

[peterjan]

With this change I hope to get rid of the following error in the log. It does not happen a lot and it happens for the same host, causing me to believe it's simply due to the host being slow and connecting to it taking longer than whatever leeway we put on the price table validity.

{"level":"error","date":"2024-01-13T03:39:48Z","component":"autopilot.accounts","msg":"failed to fund account: couldn't fund account: failed to fund account with ~500.8 mS;FundAccount: ReadResponse: failed to read price table: no price table found\n","accountID":"ed25519:614c0fa737b04dc447d39c489c8911a9bfc614ec86897d90f0053c9be152cd3f","hostKey":"ed25519:fba406818f558676e117323f45665f3affbb10bb025f74548fafe66df0dd5274","balance":"499218792671999618136517","expected":"1 SC"}

Fixes #801