upup: delete cluster should eventually give up

If it isn't making progress, eventually we should bail out so that we
can use this in scripts.  However, we don't need to be too aggressive,
because it is not good to leak resources, and a user will likely
Control-C us pretty fast when they see they're in a loop.

Issue #99

upup/pkg/kutil/delete_cluster.go

@@ -194,6 +194,7 @@ func (c *DeleteCluster) DeleteResources(resources map[string]DeletableResource)
 		glog.Infof("\t%s\t%v", k, v)
 	}
 
+	iterationsWithNoProgress := 0
 	for {
 		// TODO: Some form of default ordering based on types?
 		// TODO: Give up eventually?
@@ -258,6 +259,7 @@ func (c *DeleteCluster) DeleteResources(resources map[string]DeletableResource)
 						fmt.Printf("%s\tok\n", k)
 
 						delete(failed, k)
+						iterationsWithNoProgress = 0
 						done[k] = r
 						mutex.Unlock()
 					}
@@ -278,6 +280,12 @@ func (c *DeleteCluster) DeleteResources(resources map[string]DeletableResource)
 
 			fmt.Printf("\t%s\n", k)
 		}
+
+		iterationsWithNoProgress++
+		if iterationsWithNoProgress > 30 {
+			return fmt.Errorf("Not making progress deleting resources; giving up")
+		}
+
 		time.Sleep(10 * time.Second)
 	}
 }