simple fetchers (#1492)

* network: disable shouldNOTRequestAgain
* vendor singleflight
* network: disable shouldNOTRequestAgain
* network, storage: fix tests
* network/storage: remove HopCount and SkipCheck
* network/stream: use localstore when providing chunks a node has offered
* storage: refactor lnetstore
* storage: rename FetcherItem to Fetcher
* storage/feed: no distinction between catastrophic err or chunk not found
* network/stream: remove TestDeliveryFromNodes, as FindPeer is changed, and Swarm connectivity is not a chain
* network/stream: fixed intervals tests
* swarm: fixes for linter
* storage: use LRU cache for fetchers
* network, storage: better godoc
* storage/netstore: explicit errors
* storage/feed/lookup: Clarify ReadFunc expected return error values
* storage: address comments by elad

network/stream/streamer_test.go

@@ -93,20 +93,20 @@ func newTestClient(t string) *testClient {
 	}
 }
 
-func (self *testClient) NeedData(ctx context.Context, hash []byte) func(context.Context) error {
+func (self *testClient) NeedData(ctx context.Context, hash []byte) (bool, func(context.Context) error) {
 	self.receivedHashes[string(hash)] = hash
 	if bytes.Equal(hash, hash0[:]) {
-		return func(context.Context) error {
+		return false, func(context.Context) error {
 			<-self.wait0
 			return nil
 		}
 	} else if bytes.Equal(hash, hash2[:]) {
-		return func(context.Context) error {
+		return false, func(context.Context) error {
 			<-self.wait2
 			return nil
 		}
 	}
-	return nil
+	return false, nil
 }
 
 func (self *testClient) Close() {}