metropolis/cli/metroctl: move takeownership under cluster subcommand tree

This is in preparation for having more cluster-wide commands (same as we
keep 'node' for all node-specific commands).

Change-Id: I3fa5935e1d751261bf82a80cf61e811fa36effc9
Reviewed-on: https://review.monogon.dev/c/monogon/+/3593
Tested-by: Jenkins CI
Reviewed-by: Lorenz Brun <lorenz@monogon.tech>
diff --git a/metropolis/cli/metroctl/test/test.go b/metropolis/cli/metroctl/test/test.go
index 17f5f75..f4bba02 100644
--- a/metropolis/cli/metroctl/test/test.go
+++ b/metropolis/cli/metroctl/test/test.go
@@ -144,11 +144,12 @@
 
 	log.Printf("metroctl: Cluster's running, starting tests...")
 	st := t.Run("Init", func(t *testing.T) {
-		util.TestEventual(t, "metroctl takeownership", ctx, 30*time.Second, func(ctx context.Context) error {
+		util.TestEventual(t, "metroctl cluster takeownership", ctx, 30*time.Second, func(ctx context.Context) error {
 			// takeownership needs just a single endpoint pointing at the initial node.
 			var args []string
 			args = append(args, commonOpts...)
 			args = append(args, endpointOpts[0])
+			args = append(args, "cluster")
 			args = append(args, "takeownership")
 			return mctlFailIfMissing(t, ctx, args, "Successfully retrieved owner credentials")
 		})