IPPool with invalid "exhausted" range should be rejected

[lentzi90]

What steps did you take and what happened:

I accidentally created an IPPool with start: 192.168.0.149 and end: 192.168.0.140, (Notice how they should be the other way.) The webhook happily accepted this and then I scratched my head for half an hour wondering why the pool was "exhausted" and would not give me any IPAddresses.

What did you expect to happen:

Invalid ranges, e.g. when start > end should be rejected by the webhook with a helpful message.

Anything else you would like to add:

Environment:

• Cluster-api version:
• CAPM3 version:
• IPAM version:
• Minikube version:
• environment (metal3-dev-env or other):
• Kubernetes version: (use kubectl version):

/kind bug

[metal3-io-bot]

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