Add a little bit of uncertainty to the local channels to avoid
consuming precisely all spendable_msat on our side, which leads to
temporary channel failure if the spendable_msat changes during the
course of the payment.
Signed-off-by: Lagrang3 <lagrang3@protonmail.com>
- use switch case over all possible WIRE_* errors,
- remove the virtual machine for routefail, use a simple two step
solution: 1. update the gossip and 2. handle error cases
