mantle/podman.go: bump retry delay in podmanWorkflow test

Bump the retry delay to `10*time.Seconds` which doubles the previous
delay to allow for enough time to report success.
Update the container name in an error statement from nginx to Fedora
which should have been done in #3939

fixes: coreos/fedora-coreos-tracker#1835

mantle/kola/tests/podman/podman.go

@@ -149,12 +149,12 @@ func podmanWorkflow(c cluster.TestCluster) {
 				return err
 			}
 			if !bytes.Contains(b, []byte("TEST PAGE")) {
-				return fmt.Errorf("nginx pod is not running %s", b)
+				return fmt.Errorf("Fedora container is not running %s", b)
 			}
 			return nil
 		}
 
-		if err := util.Retry(6, 5*time.Second, podIsRunning); err != nil {
+		if err := util.Retry(6, 10*time.Second, podIsRunning); err != nil {
 			c.Fatal("Pod is not running")
 		}
 	})