addons: addressvirtual: flush macvlan addr cache when setting addrgenmode

addons: addressvirtual: flush macvlan addr cache when setting addrgenmode

When setting addrgenmode it is necessary to flap the macvlan
device. After flapping the device we also need to re-add all
the user configuration. The best way to add the user config
is to flush our internal address cache.

[10:12:10] root:~ # ifquery vlan1000
auto vlan1000
iface vlan1000
	address 192.168.10.1/24
	address fc00:10::1/64
	address-virtual 00:00:5e:00:01:01 192.168.10.1/24 fc00:10::1/64 fe80::1/64
	vlan-id 1000
	vlan-raw-device bridge

[10:12:15] root:~ # ifup -a
[10:12:24] root:~ # echo $?
0
[10:12:26] root:~ # ifquery vlan1000 -c
auto vlan1000
iface vlan1000                                                      [pass]
	vlan-raw-device bridge                                      [pass]
	vlan-id 1000                                                [pass]
	address 192.168.10.1/24                                     [pass]
	address fc00:10::1/64                                       [pass]
	address-virtual 00:00:5e:00:01:01 192.168.10.1/24 fc00:10::1/64 fe80::1/64     [pass]

[10:12:30] root:~ # ip -6 -o addr show vlan1000-v0
48: vlan1000-v0    inet6 fc00:10::1/64 scope global \       valid_lft forever preferred_lft forever
48: vlan1000-v0    inet6 fe80::200:5eff:fe00:101/64 scope link \       valid_lft forever preferred_lft forever
48: vlan1000-v0    inet6 fe80::1/64 scope link \       valid_lft forever preferred_lft forever
[10:12:33] root:~ #
[10:12:34] root:~ #
[10:12:34] root:~ # ifquery vlan1000
auto vlan1000
iface vlan1000
	address 192.168.10.1/24
	address fc00:10::1/64
	address-virtual 00:00:5e:00:01:01 192.168.10.1/24 fc00:10::1/64 fe80::1/64
	address-virtual-ipv6-addrgen off
	vlan-id 1000
	vlan-raw-device bridge

[10:12:39] root:~ #
[10:12:41] root:~ # ifreload -a -d
...
debug: vlan1000: up : running module addressvirtual
debug: vlan1000-v0: reset address cache <<<<<<<<<<<<<<<<<<<<<< without this reset ifupdown2 would be in a broken state
info: vlan1000: checking route entry ...
info: executing /bin/ip route get 192.168.10.0/24
info: netlink: ip link show dev vlan1000
info: netlink: ip link show dev vlan1000-v0
info: vlan1000-v0: netlink: ip link set dev vlan1000-v0 up
info: executing /bin/ip -force -batch - [link set dev vlan1000-v0 down
link set dev vlan1000-v0 addrgenmode none
link set dev vlan1000-v0 up
addr add 192.168.10.1/24 dev vlan1000-v0
addr add fc00:10::1/64 dev vlan1000-v0
addr add fe80::1/64 dev vlan1000-v0
]
...
[10:12:50] root:~ #
[10:12:51] root:~ # ip -6 -o addr show vlan1000-v0
48: vlan1000-v0    inet6 fc00:10::1/64 scope global \       valid_lft forever preferred_lft forever
48: vlan1000-v0    inet6 fe80::1/64 scope link \       valid_lft forever preferred_lft forever
[10:12:53] root:~ # ifquery vlan1000 -c
auto vlan1000
iface vlan1000                                                      [pass]
	vlan-raw-device bridge                                      [pass]
	vlan-id 1000                                                [pass]
	address 192.168.10.1/24                                     [pass]
	address fc00:10::1/64                                       [pass]
	address-virtual 00:00:5e:00:01:01 192.168.10.1/24 fc00:10::1/64 fe80::1/64     [pass]

[10:13:03] root:~ # echo $?
0
[10:13:04] root:~ #

Reviewed-by: Roopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: Julien Fortin <julien@cumulusnetworks.com>