test: replace calls to `kubectl apply` using `ExecShort` with `ExecMiddle` in `ciliumInstall`
test: replace calls to `kubectl apply` using `ExecShort` with `ExecMiddle` in `ciliumInstall`

Calls using `kubectl` apply shown to time out using a timeout of only 10
seconds:

```
time="2019-07-22T15:56:32Z" level=debug msg="running command: kubectl apply --filename='https://raw.githubusercontent.com/cilium/cilium/v1.5/examples/kubernetes/1.15/cilium-rbac.yaml' --dry-run"
time="2019-07-22T15:56:42Z" level=error msg="Error executing command 'kubectl apply --filename='https://raw.githubusercontent.com/cilium/cilium/v1.5/examples/kubernetes/1.15/cilium-rbac.yaml' --dry-run'" error="context deadline exceeded"
time="2019-07-22T15:56:42Z" level=error msg="Error executing command 'kubectl apply --filename='https://raw.githubusercontent.com/cilium/cilium/v1.5/examples/kubernetes/1.15/cilium-rbac.yaml' --dry-run'" error="context deadline exceeded"
cmd: "kubectl apply --filename='https://raw.githubusercontent.com/cilium/cilium/v1.5/examples/kubernetes/1.15/cilium-rbac.yaml' --dry-run" exitCode: 1 duration: 10.000253844s stdout:
time="2019-07-22T15:56:42Z" level=debug msg="running command: kubectl apply --filename='https://raw.githubusercontent.com/cilium/cilium/v1.5/examples/kubernetes/1.15/cilium-rbac.yaml' --dry-run -o yaml"
time="2019-07-22T15:56:52Z" level=error msg="Error executing command 'kubectl apply --filename='https://raw.githubusercontent.com/cilium/cilium/v1.5/examples/kubernetes/1.15/cilium-rbac.yaml' --dry-run -o yaml'" error="context deadline exceeded"
time="2019-07-22T15:56:52Z" level=error msg="Error executing command 'kubectl apply --filename='https://raw.githubusercontent.com/cilium/cilium/v1.5/examples/kubernetes/1.15/cilium-rbac.yaml' --dry-run -o yaml'" error="context deadline exceeded"
cmd: "kubectl apply --filename='https://raw.githubusercontent.com/cilium/cilium/v1.5/examples/kubernetes/1.15/cilium-rbac.yaml' --dry-run -o yaml" exitCode: 1 duration: 10.000289215s stdout:
```

Use `ExecMiddle` which has a longer timeout associated with its context to allow
for 30 seconds to pass before said commands fail.

Fixes: #8634

Signed-off by: Ian Vernon <ian@cilium.io>

tgraf/cilium,michi-covalent/cilium,tklauser/cilium,tklauser/cilium,michi-covalent/cilium,tgraf/cilium,tklauser/cilium,michi-covalent/cilium,cilium/cilium,cilium-team/cilium,tgraf/cilium,cilium/cilium,michi-covalent/cilium,cilium-team/cilium,michi-covalent/cilium,tgraf/cilium,tklauser/cilium,tklauser/cilium,cilium/cilium,cilium/cilium,tgraf/cilium,cilium/cilium,tgraf/cilium