Fix breakage when multiple default routes are declared

[andyrichardson]

About

Force parsing of single interface definition.

The issue

I'm not sure if this is normal / invalid but I was getting the following error due to having multiple default destinations

> npx -p @sitespeed.io/throttle throttle 3gslow
Using profile 3gslow
Error: Command failed: sudo tc qdisc add dev wlp0s20f3wlp0s20f3 ingress
Cannot find device "wlp0s20f3wlp0s2"

    at ChildProcess.exithandler (node:child_process:326:12)
    at ChildProcess.emit (node:events:369:20)
    at maybeClose (node:internal/child_process:1067:16)
    at Process.ChildProcess._handle.onexit (node:internal/child_process:301:5) {
  killed: false,
  code: 1,
  signal: null,
  cmd: 'sudo tc qdisc add dev wlp0s20f3wlp0s20f3 ingress',
  stdout: '',
  stderr: 'Cannot find device "wlp0s20f3wlp0s2"\n'
}

> sudo route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         OpenWrt.lan     0.0.0.0         UG    302    0        0 wlp0s20f3
default         OpenWrt.lan     0.0.0.0         UG    600    0        0 wlp0s20f3
172.17.0.0      0.0.0.0         255.255.0.0     U     0      0        0 docker0
172.18.0.0      0.0.0.0         255.255.0.0     U     0      0        0 br-672d84f52503
172.19.0.0      0.0.0.0         255.255.0.0     U     0      0        0 br-0f9d5dc90dec
192.168.1.0     0.0.0.0         255.255.255.0   U     302    0        0 wlp0s20f3
192.168.1.0     0.0.0.0         255.255.255.0   U     600    0        0 wlp0s20f3
192.168.48.0    0.0.0.0         255.255.240.0   U     0      0        0 br-bb989ac7cf64
192.168.122.0   0.0.0.0         255.255.255.0   U     0      0        0 virbr0

[soulgalore]

Thank you @andyrichardson for the fix!