[fix] handle cases where the internal-ip is already set (e.g. kubelet)

[AshleyDumaine]

Related to #111

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In the case that a Node's internal IP is already set (e.g. to a VLAN IP), the CCM will fail to set the external IP for the Node:

E1001 18:20:24.780329       1 node_controller.go:240] error syncing 'foo-control-plane-kxlgm': failed to get node modifiers from cloud provider: provided node ip for node "foo-control-plane-kxlgm" is not valid: failed to get node address from cloud provider that matches ip: 10.0.0.1, requeuing

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 56.50%. Comparing base (42e3341) to head (ff4c10f).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #236      +/-   ##
==========================================
+ Coverage   56.43%   56.50%   +0.06%     
==========================================
  Files          12       12              
  Lines        1887     1890       +3     
==========================================
+ Hits         1065     1068       +3     
  Misses        672      672              
  Partials      150      150              

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[rosskirkpat]

LGTM

[rahulait]

Should we make sure same ip is not already present in the slice? For example, if this InstanceMetadata() gets called again after 5-10 mins, then we'll end up adding all the existing ip's again into the slice. Not sure if k8s automatically handles such case.

[AshleyDumaine]

It doesn't matter if it is, it just needs to be present: https://github.com/kubernetes/cloud-provider/blob/master/node/helpers/address.go#L114-L135

[rahulait]

lgtm