Clarify kubelet_dockershim_nodocker error message

Clarify the error message returned when trying to use the docker runtime
on a Kubelet that was compiled without Docker.

We removed the "w/" and "w/o", which can be confusing abbreviations, and
also add slightly more detail on the actual error.

Author: mattjmcnaughton

pkg/kubelet/kubelet_dockershim_nodocker.go

@@ -32,5 +32,5 @@ func runDockershim(kubeCfg *kubeletconfiginternal.KubeletConfiguration,
 	remoteImageEndpoint string,
 	nonMasqueradeCIDR string) error {
 
-	return fmt.Errorf("trying to use docker runtime, w/ Kubelet compiled w/o docker support")
+	return fmt.Errorf("trying to use docker runtime when Kubelet was compiled without docker support")
 }