Clean up parameters in e2e tests

[justinsb]

#5138 now uses the gce_zone parameter as the zone for AWS also.

We should figure out which parameters have genuine meaning across clouds and can be shared, and rename them (gce_zone -> cloud_zone or just zone) This will likely break the scripts etc that set these flags though, so we have to be careful.

[lavalamp]

Yeah, it definitely feels pretty weird to use gce_zone both places.

[fejta]

/close

[k8s-ci-robot]

@fejta: you can't close an issue unless you authored it or you are assigned to it.

In response to this:

/close

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