bond: Only drop packets that indicate moves on SLB bonds.

bond: Only drop packets that indicate moves on SLB bonds.

SLB bonds, for important reasons, drop most incoming packets that indicate
that a MAC has moved to the bond from another port.  These reasons do not
apply to other types of bonds, but until now OVS has still dropped them.

This fixes the problem.  It changes behavior of active-backup bonds and
stable bonds, neither of which has the same problem as SLB.  Behavior of
SLB bonds and TCP bonds in SLB fallback mode is unaffected.

Bug #7928.