swarm/network/stream: add syncing test (#1399)

* swarm/network/stream: remove old syncing test and replace it with two more granular tests, with the first one testing a full sync between two nodes (makes sure that when all subscriptions are established on all bins - all content is replicated from one node to the other), and a second test that adds a bigger amount of nodes to a star network topology, effectively making the pivot node have a depth > 0 to sync just certain content to the connected nodes (due to a star topology this test (always 1 hop) does not check that, for example, specific content is routed across multiple nodes, but assumes content should be only on the most proximate node)

* api, cmd/swarm-smoke, fuse, network, storage: fix data dir leak when using ephemeral filestore, pull test params to be easily adjustable

api/api_test.go

@@ -53,10 +53,11 @@ func testAPI(t *testing.T, f func(*API, *chunk.Tags, bool)) {
 		}
 		defer os.RemoveAll(datadir)
 		tags := chunk.NewTags()
-		fileStore, err := storage.NewLocalFileStore(datadir, make([]byte, 32), tags)
+		fileStore, cleanup, err := storage.NewLocalFileStore(datadir, make([]byte, 32), tags)
 		if err != nil {
 			return
 		}
+		defer cleanup()
 		api := NewAPI(fileStore, nil, nil, nil, tags)
 		f(api, tags, v)
 	}