Description of problem:
Create two virtual networks which are "IPv6 only" and "IPv4 and IPv6". Then import two shutoff vm with fedora 31 and change their network interface source to the network which is "IPv4 and IPv6". Then run the two VM, after that check which VM has inet and inet6 in its "IP address" of the network interface tab. then shut off this VM and change its network interface source to the network which is "IPv6 only". Then re-run this VM, its "IP address" of the network interface tab will still contain two IP addresses.


Version-Release number of selected components (if applicable):
cockpit-258-1.el9.x86_64
cockpit-machines-256-1.el9.noarch
libvirt-dbus-1.4.1-5.el9.x86_64

How reproducible:
100%


Steps to Reproduce:
1 Create IPv6 only network like follow and activate it:
Connection       system
Name                IPv6
Forward mode   NAT
Device                Automatic
IP configuration  IPv6 only
IPv6 address      FEC0:0:0:8000::1
Prefix length       64
Set DHCP range  checked
    Start FEC0:0:0:8000::2   End FEC0:0:0:8000::242
2 Create IPv4 and IPv6 network like follow and activate it:
Connection       system
Name                IPv4v6
Forward mode   NAT
Device                Automatic
IP configuration  IPv4 and IPv6
IPv4 address      192.168.100.1
Mask or prefix length  24
Set DHCP range          checked
    Start 192.168.100.2    End 192.168.100.254
IPv6 address      FEC0:0:0:8001::1
Prefix length       64
Set DHCP range  checked
    Start FEC0:0:0:8001::2   End FEC0:0:0:8001::252
3 Import two shutoff VM with fedora 31
4 Change the VMs network interface source to "IPv4v6"
5 Run the two VMs
6 Enter the VM detail page which shows two IP addresses in network interface tab
7 Shut off the VM in step 6
8 Change network interface source of the VM in step 6 to "IPv6"
9 Re-run the VM


Actual results:
1 After step 9, "IP address" in network interface tab will still contain two IP addresses


Expected results:
1 After step 9, "IP address" in network interface tab should contain only IPv6 address


Additional info: