Make client.Request more testable, break coupling with RESTClient

Moves polling to a function provided by the RESTClient, not innate
to Request. Moves doRequest from RESTClient to Request for clarity.

pkg/api/types.go

@@ -603,6 +603,7 @@ type Status struct {
 type StatusDetails struct {
 	// The ID attribute of the resource associated with the status StatusReason
 	// (when there is a single ID which can be described).
+	// TODO: replace with Name
 	ID string `json:"id,omitempty" yaml:"id,omitempty"`
 	// The kind attribute of the resource associated with the status StatusReason.
 	// On some operations may differ from the requested resource Kind.