Bug 167793

System leak mbufs with multicast arp adresses

Fix: 

Don't use large number multicast arp adressed in one LAN.
How-To-Repeat: Create in one box static arp table for 65533 entries 172.16.0.0/16 with
multicast arp adresses, example eb:ee:00:00:xx:yy. xx yy - count number.
From another box after time we will see:

root samnote# netstat -m
*26078/427/26505 mbufs in use (current/cache/total)
*26076/170/26246/65536 mbuf clusters in use (current/cache/total/max)
*26076/164 mbuf+clusters out of packet secondary zone in use (current/cache)
0/20/20/65536 4k (page size) jumbo clusters in use (current/cache/total/max)
0/0/0/6400 9k jumbo clusters in use (current/cache/total/max)
0/0/0/3200 16k jumbo clusters in use (current/cache/total/max)
*58671K/526K/59198K bytes allocated to network (current/cache/total)
0/0/0 requests for mbufs denied (mbufs/clusters/mbuf+clusters)
0/0/0 requests for jumbo clusters denied (4k/9k/16k)
0/5/6656 sfbufs in use (current/peak/max)
0 requests for sfbufs denied
0 requests for sfbufs delayed
0 requests for I/O initiated by sendfile
0 calls to protocol drain routines

* values will increment. after some hours network stack will fail with
error: not free mbuf. By this bug I make DDOS for myself.