cmd/swarm: fix resource leaks in tests (#19443)

* swarm/api: fix file descriptor leak in NewTestSwarmServer

Swarm storage (localstore) was not closed. That resulted a
"too many open files" error if `TestClientUploadDownloadRawEncrypted`
was run with `-count 1000`.

* cmd/swarm: speed up StartNewNodes() by parallelization

Reduce cluster startup time from 13s to 7s.

* swarm/api: disable flaky TestClientUploadDownloadRawEncrypted with -race

* swarm/storage: disable flaky TestLDBStoreCollectGarbage (-race)

With race detection turned on the disabled cases often fail with:
"ldbstore_test.go:535: expected surplus chunk 150 to be missing, but got no error"

* cmd/swarm: fix process leak in TestACT and TestSwarmUp

Each test run we start 3 nodes, but we did not terminate them. So
those 3 nodes continued eating up 1.2GB (3.4GB with -race) after test
completion.

6b6c4d1c27 changed how we start clusters
to speed up tests. The changeset merged together test cases
and introduced a global cluster. But "forgot" about termination.

Let's get rid of "global cluster" so we have a clear owner of
termination (some time sacrifice), while leaving subtests to use the
same cluster.

cmd/swarm/access_test.go

@@ -52,11 +52,12 @@ func TestACT(t *testing.T) {
 		t.Skip()
 	}
 
-	initCluster(t)
+	cluster := newTestCluster(t, clusterSize)
+	defer cluster.Shutdown()
 
 	cases := []struct {
 		name string
-		f    func(t *testing.T)
+		f    func(t *testing.T, cluster *testCluster)
 	}{
 		{"Password", testPassword},
 		{"PK", testPK},
@@ -65,7 +66,9 @@ func TestACT(t *testing.T) {
 	}
 
 	for _, tc := range cases {
-		t.Run(tc.name, tc.f)
+		t.Run(tc.name, func(t *testing.T) {
+			tc.f(t, cluster)
+		})
 	}
 }
 
@@ -74,7 +77,7 @@ func TestACT(t *testing.T) {
 // The parties participating - node (publisher), uploads to second node then disappears. Content which was uploaded
 // is then fetched through 2nd node. since the tested code is not key-aware - we can just
 // fetch from the 2nd node using HTTP BasicAuth
-func testPassword(t *testing.T) {
+func testPassword(t *testing.T, cluster *testCluster) {
 	dataFilename := testutil.TempFileWithContent(t, data)
 	defer os.RemoveAll(dataFilename)
 
@@ -226,7 +229,7 @@ func testPassword(t *testing.T) {
 // The parties participating - node (publisher), uploads to second node (which is also the grantee) then disappears.
 // Content which was uploaded is then fetched through the grantee's http proxy. Since the tested code is private-key aware,
 // the test will fail if the proxy's given private key is not granted on the ACT.
-func testPK(t *testing.T) {
+func testPK(t *testing.T, cluster *testCluster) {
 	dataFilename := testutil.TempFileWithContent(t, data)
 	defer os.RemoveAll(dataFilename)
 
@@ -359,13 +362,13 @@ func testPK(t *testing.T) {
 }
 
 // testACTWithoutBogus tests the creation of the ACT manifest end-to-end, without any bogus entries (i.e. default scenario = 3 nodes 1 unauthorized)
-func testACTWithoutBogus(t *testing.T) {
-	testACT(t, 0)
+func testACTWithoutBogus(t *testing.T, cluster *testCluster) {
+	testACT(t, cluster, 0)
 }
 
 // testACTWithBogus tests the creation of the ACT manifest end-to-end, with 100 bogus entries (i.e. 100 EC keys + default scenario = 3 nodes 1 unauthorized = 103 keys in the ACT manifest)
-func testACTWithBogus(t *testing.T) {
-	testACT(t, 100)
+func testACTWithBogus(t *testing.T, cluster *testCluster) {
+	testACT(t, cluster, 100)
 }
 
 // testACT tests the e2e creation, uploading and downloading of an ACT access control with both EC keys AND password protection
@@ -373,7 +376,7 @@ func testACTWithBogus(t *testing.T) {
 // set and also protects the ACT with a password. the third node should fail decoding the reference as it will not be granted access.
 // the third node then then tries to download using a correct password (and succeeds) then uses a wrong password and fails.
 // the publisher uploads through one of the nodes then disappears.
-func testACT(t *testing.T, bogusEntries int) {
+func testACT(t *testing.T, cluster *testCluster, bogusEntries int) {
 	var uploadThroughNode = cluster.Nodes[0]
 	client := swarmapi.NewClient(uploadThroughNode.URL)