use relative path instead of $PWD for go:generate (for go 1.17 compatibility) (#1615)

pkg/util/httpclient/httpclient.go

 package httpclient
 
-//go:generate mockgen -package mocks -destination=$PWD/mocks/$GOFILE -source=$GOFILE -build_flags=-mod=vendor
+//go:generate mockgen -package mocks -destination=../../../mocks/$GOFILE -source=$GOFILE -build_flags=-mod=vendor
 
 import "net/http"
 

pkg/util/volumes/volumes.go

 package volumes
 
-//go:generate mockgen -package mocks -destination=$PWD/mocks/$GOFILE -source=$GOFILE -build_flags=-mod=vendor
+//go:generate mockgen -package mocks -destination=../../../mocks/$GOFILE -source=$GOFILE -build_flags=-mod=vendor
 
 import v1 "k8s.io/api/core/v1"