🌱 Allows configuring crossZoneLoadBalancing on controlPlaneLoadBalancer

[gab-satchi]

• removed omit empty on the field so it still shows up when set to false

Fixes #1754

[randomvariable]

Could also a test to loadbalancer_test.go that s.configureAttributes does indeed get called when the CrossZoneLoadBalancing attribute is changed. WDYT

[gab-satchi]

the configureAttributes is just a private method so testing that's called alone may not be valuable. Adding tests around ensuring the correct AWS calls are made might be better. I think AWSMachine controller tests do a decent job at that so could do something similar with cluster. Created #1804

[randomvariable]

SGTM. Merging this in and treat #1804 separately.
/lgtm
/approve

[k8s-ci-robot]

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