Chowning no longer breaks integration tests

- if we try to really chown to group vcap when no such group exists, it
would be broken in CI
- now, we don't do that when running tests

[#154423151](https://www.pivotaltracker.com/story/show/154423151)

Signed-off-by: Joshua Aresty <joshua.aresty@emc.com>

main/agent.go

@@ -9,6 +9,7 @@ import (
 
 	boshapp "github.com/cloudfoundry/bosh-agent/app"
 	"github.com/cloudfoundry/bosh-agent/infrastructure/agentlogger"
+	"github.com/cloudfoundry/bosh-agent/platform"
 	"github.com/cloudfoundry/bosh-utils/logger"
 	boshlog "github.com/cloudfoundry/bosh-utils/logger"
 	boshsys "github.com/cloudfoundry/bosh-utils/system"
@@ -25,6 +26,10 @@ func runAgent(opts boshapp.Options, logger logger.Logger) chan error {
 		logger.Debug(mainLogTag, "Starting agent")
 
 		fs := boshsys.NewOsFileSystem(logger)
+		if opts.PlatformName == "dummy" {
+			fs = platform.DummyWrapFs(fs)
+		}
+
 		app := boshapp.New(logger, fs)
 
 		err := app.Setup(opts)

platform/dummy_wrap_fs.go

@@ -0,0 +1,19 @@
+package platform
+
+import boshsys "github.com/cloudfoundry/bosh-utils/system"
+
+var _ boshsys.FileSystem = &DummyFs{}
+
+func DummyWrapFs(fs boshsys.FileSystem) boshsys.FileSystem {
+	return &DummyFs{
+		FileSystem: fs,
+	}
+}
+
+type DummyFs struct {
+	boshsys.FileSystem
+}
+
+func (d *DummyFs) Chown(path string, username string) error {
+	return nil
+}