enable GO111MODULE also on go test (zalando#701)

* enable GO111MODULE also on go test

Author: FxKu

Makefile

@@ -93,7 +93,7 @@ deps:
 
 test:
 	hack/verify-codegen.sh
-	@go test ./pkg/...
+	GO111MODULE=on go test ./...
 
 e2e: docker # build operator image to be tested
 	cd e2e; make tools test clean

delivery.yaml

@@ -32,7 +32,7 @@ pipeline:
         - desc: 'Run unit tests'
           cmd: |
             export PATH=$PATH:$HOME/go/bin
-            go test ./pkg/...
+            go test ./...
         - desc: 'Run e2e tests'
           cmd: |
             make e2e