`networkperf` suite fails on `amd64` due to the inclusion of the `n4-standard-16` machine type

This suite unfortunately fails altogether (i.e. no test results, just the `daisy.log`) due to the inclusion of `n4-standard-16`:

```
...
...
"[networkperf.create-vms]: CreateInstances: Creating instance "servervmt2dstandard1-networkperf-1tmz4".
[networkperf]: Error running workflow: step "create-vms" run error: googleapi: Error 400: [pd-balanced, n4-standard-16] features are not compatible for creating instance., badRequest"
```

so I pushed a branch to my forked repo with `n4-standard-16` dropped and it does actually run the tests then.

However, there were still a handful of failures across `TestNetworkPerformance` over the different machine types, but curiously the `FAILURE` messages were: `Expected: 85 Gbits/s, Actual: 94.7 Gbits/s` (as an example). Which doesn't seem like a true failure if it's exceeding the expected target? In the code the if statement is `if resultPerf < expected` so I wonder if the output is being mangled perhaps?