manifest: remove explicit ownership from insights files

When creating the service drop-in file and directory for running the
insights client on boot, don't specify ownership.  This is for the same
reasons as for the other files we create in the subscription pipeline:
there is no `chown` binary in the subscription pipeline tree, which
would be required to explicitly set the file's ownership.

Update tests to match.

pkg/manifest/subscription.go

@@ -195,11 +195,16 @@ func runInsightsClientOnBoot() (*fsnode.Directory, *fsnode.File, error) {
 	// all the options we need. This is a temporary workaround
 	// until we get the stage updated to support everything we need.
 	icDropinFilepath, icDropinContents := insightsClientDropin()
-	icDropinDirectory, err := fsnode.NewDirectory(filepath.Dir(icDropinFilepath), nil, "root", "root", true)
+
+	// NOTE: Ownership is left as nil:nil, which implicitly creates files as
+	// root:root. Adding an explicit owner requires chroot to run the
+	// org.osbuild.chown stage, which we can't run in the subscription pipeline
+	// since it has no packages.
+	icDropinDirectory, err := fsnode.NewDirectory(filepath.Dir(icDropinFilepath), nil, nil, nil, true)
 	if err != nil {
 		return nil, nil, err
 	}
-	icDropinFile, err := fsnode.NewFile(icDropinFilepath, nil, "root", "root", []byte(icDropinContents))
+	icDropinFile, err := fsnode.NewFile(icDropinFilepath, nil, nil, nil, []byte(icDropinContents))
 	if err != nil {
 		return nil, nil, err
 	}

pkg/manifest/subscription_test.go

@@ -407,7 +407,7 @@ Requisite=greenboot-healthcheck.service
 After=network-online.target greenboot-healthcheck.service osbuild-first-boot.service
 [Install]
 WantedBy=multi-user.target`
-	icDropinFile, err := fsnode.NewFile("/etc/systemd/system/insights-client.service.d/override.conf", nil, "root", "root", []byte(dropinContents))
+	icDropinFile, err := fsnode.NewFile("/etc/systemd/system/insights-client.service.d/override.conf", nil, nil, nil, []byte(dropinContents))
 	if err != nil {
 		panic(err)
 	}
@@ -416,7 +416,7 @@ WantedBy=multi-user.target`
 
 func mkInsightsDropinDir() *fsnode.Directory {
 
-	icDropinDirectory, err := fsnode.NewDirectory("/etc/systemd/system/insights-client.service.d", nil, "root", "root", true)
+	icDropinDirectory, err := fsnode.NewDirectory("/etc/systemd/system/insights-client.service.d", nil, nil, nil, true)
 	if err != nil {
 		panic(err)
 	}