Don't use global state

[ericchiang]

https://github.com/coreos/operator-sdk/blob/01a1d22496f3344e750234bde022f7565d5d0fbe/pkg/k8sclient/client.go#L37-L45

https://peter.bourgon.org/blog/2017/06/09/theory-of-modern-go.html

[mikewied]

This issue blocks #139. I haven't looked into dynamic client pools, but it looks like once you create the client pool the any CRD's registered after the operator starts won't be available to the sdkclient API's.

[ericchiang]

cc @rithujohn191