Support adding tags to nodebalancers

[tchinmai7]

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Support adding tags to a nodebalancer - supply a comma-separated string in an annotation to a service of type LoadBalancer to automatically add tags to the created node-balancer resource. Fixes #137

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[okokes-akamai]

This only covers the creation path, what about the [uU]pdateNodeBalancer flow - I'd think we want to support that as well? I.e. annotation gets updated -> NB gets their tags updated as well.

[tchinmai7]

This only covers the creation path, what about the [uU]pdateNodeBalancer flow - I'd think we want to support that as well? I.e. annotation gets updated -> NB gets their tags updated as well.

good catch - will update