circuit_package_relay_cell failed. Closing.

We merged !807 (merged) yesterday and this bug warning is showing up.

log_warn(LD_BUG,"circuit_package_relay_cell failed. Closing.");

This is actually normal that it starts showing because before it couldn't fail but now it can because the append cell to a circuit can fail if the circuit queue is maxed out which logs on protocol level.

So we should just remove that log_warn in my opinion in favor of more specific error log when circuit_package_relay_cell() is failing.