unit test for driver fail with newer golang such as v1.11

[nak3]

Issue

Unit test for driver fail with golang v1.11.

Steps to reproduce

$ go version
go version go1.11.2 linux/amd64

$ GOOS=linux CGO_ENABLED=1 go test -v -cover -race -timeout 10s ./plugins/routed-eni/driver
# github.com/aws/amazon-vpc-cni-k8s/plugins/routed-eni/driver
plugins/routed-eni/driver/driver.go:184: Wrapf call has arguments but no formatting directives
FAIL	github.com/aws/amazon-vpc-cni-k8s/plugins/routed-eni/driver [build failed]

Additionl info

golang 1.10.3 works fine. (So, I'm sorry if this project does not support golang v1.11 for now.)

$ go version
go version go1.10.3 linux/amd64

$ GOOS=linux CGO_ENABLED=1 go test -cover -race -timeout 10s ./plugins/routed-eni/driver
ok  	github.com/aws/amazon-vpc-cni-k8s/plugins/routed-eni/driver	1.018s	coverage: 62.3% of statements

Proposal fix #241