[Bug 270478] Duplicated ARP reply sent from if_bridge member

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=270478

            Bug ID: 270478
           Summary: Duplicated ARP reply sent from if_bridge member
           Product: Base System
           Version: CURRENT
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: kern
          Assignee: bugs@FreeBSD.org
          Reporter: zlei@FreeBSD.org

Observed the problem while repeating
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=240106#c28

A script to repeat:

```
#!/bin/sh

kldload -nq if_bridge

epa=$( ifconfig epair create )
epb=${epa%a}b


j=$( jail -ic vnet persist )
ifconfig $epb vnet $j
b=$( jexec $j ifconfig bridge create )
jexec $j ifconfig $b addm $epb
jexec $j ifconfig $epb up
jexec $j ifconfig $b inet 192.168.2.2/24
ifconfig $epa inet 192.168.2.1/24

# pre populate arp table for jail
jexec $j ping -qc1 192.168.2.1

# print interfaces
ifconfig $epa
jexec $j ifconfig $epb
jexec $j ifconfig $b

tmp=$( mktemp )
nohup tcpdump -i $epa -Uw $tmp > /dev/null &

# clear host arp table, and trigger an arp request via ping
arp -da
sleep 1
ping -c1 192.168.2.2

# wait a little for tcpdump to write all packets
sleep 2
kill $!

# show arp table in jail
jexec $j arp -na

jail -R $j
ifconfig $epa destroy

tcpdump -ennv -r $tmp 'arp or icmp'
rm $tmp
```

The output:
=====================
PING 192.168.2.1 (192.168.2.1): 56 data bytes

--- 192.168.2.1 ping statistics ---
1 packets transmitted, 1 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 0.181/0.181/0.181/0.000 ms
epair0a: flags=8863<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
        options=8<VLAN_MTU>
        ether 02:30:35:63:2b:0a
        inet 192.168.2.1 netmask 0xffffff00 broadcast 192.168.2.255
        groups: epair
        media: Ethernet 10Gbase-T (10Gbase-T <full-duplex>)
        status: active
        nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
epair0b: flags=8963<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> metric 0
mtu 1500
        options=8<VLAN_MTU>
        ether 02:30:35:63:2b:0b
        groups: epair
        media: Ethernet 10Gbase-T (10Gbase-T <full-duplex>)
        status: active
        nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
bridge0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
        ether ea:80:d1:f2:05:ae
        inet 192.168.2.2 netmask 0xffffff00 broadcast 192.168.2.255
        id 00:00:00:00:00:00 priority 32768 hellotime 2 fwddelay 15
        maxage 20 holdcnt 6 proto rstp maxaddr 2000 timeout 1200
        root id 00:00:00:00:00:00 priority 32768 ifcost 0 port 0
        member: epair0b flags=143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
                ifmaxaddr 0 port 2 priority 128 path cost 2000
        groups: bridge
        nd6 options=9<PERFORMNUD,IFDISABLED>
192.168.2.2 (192.168.2.2) deleted
PING 192.168.2.2 (192.168.2.2): 56 data bytes
64 bytes from 192.168.2.2: icmp_seq=0 ttl=64 time=0.155 ms

--- 192.168.2.2 ping statistics ---
1 packets transmitted, 1 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 0.155/0.155/0.155/0.000 ms
? (192.168.2.2) at ea:80:d1:f2:05:ae on bridge0 permanent [bridge]
? (192.168.2.1) at 02:30:35:63:2b:0a on bridge0 expires in 1198 seconds
[bridge]
reading from file /tmp/tmp.WKOgI9yi, link-type EN10MB (Ethernet)
01:59:02.272912 02:30:35:63:2b:0a > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806),
length 42: Ethernet (len 6), IPv4 (len 4), Request who-has 192.168.2.2 tell
192.168.2.1, length 28
01:59:02.272963 ea:80:d1:f2:05:ae > 02:30:35:63:2b:0a, ethertype ARP (0x0806),
length 42: Ethernet (len 6), IPv4 (len 4), Reply 192.168.2.2 is-at
ea:80:d1:f2:05:ae, length 28
01:59:02.272969 02:30:35:63:2b:0a > ea:80:d1:f2:05:ae, ethertype IPv4 (0x0800),
length 98: (tos 0x0, ttl 64, id 34746, offset 0, flags [none], proto ICMP (1),
length 84)
    192.168.2.1 > 192.168.2.2: ICMP echo request, id 27667, seq 0, length 64
01:59:02.272971 02:30:35:63:2b:0b > 02:30:35:63:2b:0a, ethertype ARP (0x0806),
length 42: Ethernet (len 6), IPv4 (len 4), Reply 192.168.2.2 is-at
02:30:35:63:2b:0b, length 28
01:59:02.273013 ea:80:d1:f2:05:ae > 02:30:35:63:2b:0a, ethertype IPv4 (0x0800),
length 98: (tos 0x0, ttl 64, id 33683, offset 0, flags [none], proto ICMP (1),
length 84)
    192.168.2.2 > 192.168.2.1: ICMP echo reply, id 27667, seq 0, length 64

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