[cable-guy] Config mismatch loop after disabling DHCP backup server

BlueOS 1.4.3-beta.4

I disabled the DHCP backup server using the interface and got a loop of config mismatch.

`ifconfig`:
```bash
docker0: flags=4163 mtu 1500 [0/0]
inet 172.18.0.1 netmask 255.255.0.0 broadcast 172.18.255.255
ether 56:32:03:cf:29:40 txqueuelen 0 (Ethernet)
RX packets 8335 bytes 20367925 (19.4 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 39822 bytes 8410732 (8.0 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
eth0: flags=4163 mtu 1500
inet 192.168.2.2 netmask 255.255.255.0 broadcast 0.0.0.0
ether 2c:cf:67:21:e2:ab txqueuelen 1000 (Ethernet)
RX packets 970669 bytes 1328916542 (1.2 GiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 94632 bytes 126946366 (121.0 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
device interrupt 106

lo: flags=73 mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10
loop txqueuelen 1000 (Local Loopback)
RX packets 371182 bytes 140066597 (133.5 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 371182 bytes 140066597 (133.5 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

uap0: flags=4163 mtu 1500
inet 192.168.42.1 netmask 255.255.255.0 broadcast 192.168.42.255
ether 2e:cf:67:81:e2:ac txqueuelen 1000 (Ethernet)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 98 bytes 7573 (7.3 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

usb0: flags=4099 mtu 1500
inet 192.168.3.1 netmask 255.255.255.0 broadcast 0.0.0.0
ether 1a:41:c2:6b:7d:ed txqueuelen 1000 (Ethernet)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

vethe5acd9e: flags=4163 mtu 1500
ether c2:fd:7a:6b:d6:9f txqueuelen 0 (Ethernet)
RX packets 8335 bytes 20484615 (19.5 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 39822 bytes 8410732 (8.0 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

wlan0: flags=4099 mtu 1500
ether 2c:cf:67:21:e2:ac txqueuelen 1000 (Ethernet)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
```

`route`:
```bash
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
default 192.168.2.1 0.0.0.0 UG 2000 0 0 eth0
172.18.0.0 0.0.0.0 255.255.0.0 U 0 0 0 docker0
192.168.2.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
192.168.2.2 0.0.0.0 255.255.255.255 UH 0 0 0 eth0
192.168.2.255 0.0.0.0 255.255.255.255 UH 0 0 0 eth0
192.168.3.0 0.0.0.0 255.255.255.0 U 0 0 0 usb0
192.168.42.0 0.0.0.0 255.255.255.0 U 0 0 0 uap0
224.0.0.0 0.0.0.0 240.0.0.0 U 0 0 0 eth0
```

`cat ~/.config/cable-guy/settings-2.json`:
```
───────┬─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
│ File: /root/.config/cable-guy/settings-2.json
───────┼─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
1 │ {
2 │ "VERSION": 2,
3 │ "content": [
4 │ {
5 │ "name": "usb0",
6 │ "addresses": [
7 │ {
8 │ "ip": "192.168.3.1",
9 │ "mode": "server"
10 │ }
11 │ ],
12 │ "info": null,
13 │ "priority": null,
14 │ "routes": []
15 │ },
16 │ {
17 │ "name": "eth0",
18 │ "addresses": [
19 │ {
20 │ "ip": "0.0.0.0",
21 │ "mode": "client"
22 │ },
23 │ {
24 │ "ip": "192.168.2.2",
25 │ "mode": "unmanaged"
26 │ }
27 │ ],
28 │ "info": {
29 │ "connected": true,
30 │ "number_of_disconnections": 0,
31 │ "priority": 0
32 │ },
33 │ "priority": null,
34 │ "routes": [
35 │ {
36 │ "destination": "224.0.0.0/4",
37 │ "gateway": null,
38 │ "priority": null,
39 │ "managed": true
40 │ },
41 │ {
42 │ "destination": "192.168.2.255/32",
43 │ "gateway": null,
44 │ "priority": null,
45 │ "managed": false
46 │ },
47 │ {
48 │ "destination": "192.168.2.2/32",
49 │ "gateway": null,
50 │ "priority": null,
51 │ "managed": false
52 │ },
53 │ {
54 │ "destination": "ff00::/8",
55 │ "gateway": null,
56 │ "priority": 1024,
57 │ "managed": false
58 │ },
59 │ {
60 │ "destination": "192.168.2.0/24",
61 │ "gateway": null,
62 │ "priority": null,
63 │ "managed": false
64 │ }
65 │ ]
66 │ }
67 │ ]
68 │ }
───────┴─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
```