Reserve ILB IP address before deleting FR on protocol change

[panslava]

This fixes a bug, which could result in losing ip address. On Service Protocol change, we delete forwarding rule before changing Backend Service. But we didn't reserve address before forwarding rule rule deletion, so after deleting forwarding rule, this address could be reserved from some other place.

[aojea]

no tests?

[panslava]

it's hard, maybe, I need to add a hook for fake gce, and check on forwarding rule deletion, that address of the forwarding rule is reserved

[aojea]

it's hard, maybe, I need to add a hook for fake gce, and check on forwarding rule deletion, that address of the forwarding rule is reserved

and an e2e instead?

[cezarygerard]

there is a line of code in thatd does not follow the best practices:
pkg/loadbalancers/forwarding_rules.go:ensureForwardingRule

	equal, err := Equal(existingFwdRule, fr)
	if err != nil {
		return existingFwdRule, err
	}

please change it to

	equal, err := Equal(existingFwdRule, fr)
	if err != nil {
		return nil, err
	}

[cezarygerard]

Please also add the unit test for address reservation

[panslava]

Added unit tests, with adding hook on forwarding rule deletion which checks that address is reserved before deletion

[panslava]

And btw, the added code in unit tests is failing on master, as expected

[cezarygerard]

/lgtm

[k8s-ci-robot]

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