Allow sessionAffinity for the SolrCloud CommonService

[HoustonPutman]

Kubernetes ClusterIP Services allow for sessionAffinity, and customization of the max session stickiness timeout.

More information can be found here: https://kubernetes.io/docs/reference/networking/virtual-ips/#session-affinity

All we would need is these options to be given under SolrCloud.Spec.customSolrKubeOptions.commonServiceOptions, and then passed to the service. This doesn't make sense for the headless service or node services.

[trevorpburke]

Took a pass at this in #571

Just started learning Go this week, but imagine I'm missing a step or two here. LMK!