lacp: Remove racy kassert

In lacp_select_tx_port_by_hash(), we assert that the selected port is
DISTRIBUTING. However, the port state is protected by the LACP_LOCK(),
which is not held around lacp_select_tx_port_by_hash().  So this
assertion is racy, and can result in a spurious panic when links
are flapping.

It is certainly possible to fix it by acquiring LACP_LOCK(),
but this seems like an early development assert, and it seems best
to just remove it, rather than add complexity inside an ifdef
INVARIANTS.

Sponsored by: Netflix
Reviewed by: hselasky
Differential Revision: https://reviews.freebsd.org/D35396

sys/net/ieee8023ad_lacp.c

@@ -876,9 +876,6 @@ lacp_select_tx_port_by_hash(struct lagg_softc *sc, uint32_t hash,
 	hash %= count;
 	lp = map[hash];
 
-	KASSERT((lp->lp_state & LACP_STATE_DISTRIBUTING) != 0,
-	    ("aggregated port is not distributing"));
-
 	return (lp->lp_lagg);
 }