Allow KubectlBuildWrapper to work when k8s API server is behind firewall#599

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Wilkhu90 wants to merge 2 commits intojenkinsci:masterfrom

Wilkhu90:master

Commits on Sep 19, 2019

Adding changes to accomodate to situation when kubernetes API server is behind firewall
swilkhu
committed

Commits on Sep 26, 2019

Adding changes based on recommendations from reviewer(s)
swilkhu
committed