Test the following cases, on x86-64 and riscv hardwares:
# kenv, load modules, create new vnets
# create vnet, then kenv && load modules
# kenv && load modules, check vnet0 (the host)
```
#!/bin/sh
# unload it incase it is already loaded
kldstat -qm if_bridge && kldunload if_bridge
j1=$( jail -ic vnet persist )
# The default is 1, we set it to 0 in system envionment
echo "set system envionment"
kenv net.link.bridge.pfil_member=0
kldload if_bridge
echo "sysctl in host (vnet0)"
sysctl net.link.bridge.pfil_member
echo "sysctl in vnet $j1"
jexec $j1 sysctl net.link.bridge.pfil_member
j2=$( jail -ic vnet persist )
echo "sysctl in new vnet $j2"
jexec $j2 sysctl net.link.bridge.pfil_member
kldunload if_bridge
jail -R $j2
jail -R $j1
```
Before this change:
```
set system envionment
net.link.bridge.pfil_member="0"
sysctl in host (vnet0)
net.link.bridge.pfil_member: 1
sysctl in vnet 1
net.link.bridge.pfil_member: 1
sysctl in new vnet 2
net.link.bridge.pfil_member: 1
```
after:
```
set system envionment
net.link.bridge.pfil_member="0"
sysctl in host (vnet0)
net.link.bridge.pfil_member: 0
sysctl in vnet 1
net.link.bridge.pfil_member: 0
sysctl in new vnet 2
net.link.bridge.pfil_member: 0
```