LACP: Do not wait response for marker messages not sent

The error returned when a marker message can not be emitted on a port is not handled.

This cause the lacp to block all emissions until the timeout of 3 seconds is reached.

To fix this issue, I just clear the LACP_PORT_MARK flag when the packet could not be emitted.

Differential revision: https://reviews.freebsd.org/D30467
Obtained from: Stormshield