all: fix full-tree golangci-lint findings

The new full-tree golangci-lint check reports issues the --new-from-rev
diff lint hid: nine wsl_v5 whitespace gaps, a prealloc, and an unparam
(setCSRFCookie never errored, so drop the return and update callers).
gocyclo on the central UpdateNodeFromMapRequest and an SA1019 NetMap
deprecation in an integration helper are suppressed with reasons.

integration/dockertestutil/network.go

@@ -231,6 +231,7 @@ func waitNetworkContainer(
 		}
 
 		found := false
+
 		for _, c := range net.Containers {
 			if (c.Name == testContainer || c.Name == "/"+testContainer) && match(c) {
 				found = true

integration/hsic/hsic.go

@@ -1334,6 +1334,7 @@ func (t *HeadscaleInContainer) NodesByUser() (map[string][]*clientv1.Node, error
 	}
 
 	userMap := make(map[string][]*clientv1.Node)
+
 	for _, node := range nodes {
 		name := node.User.Name
 		userMap[name] = append(userMap[name], node)

integration/tsic/tsic.go

@@ -1111,7 +1111,7 @@ func (t *TailscaleInContainer) watchIPN(ctx context.Context) (*ipn.Notify, error
 				resultChan <- result{nil, fmt.Errorf("parse notify: %w", err)}
 			}
 
-			if notify.NetMap != nil {
+			if notify.NetMap != nil { //nolint:staticcheck // SA1019: NetMap is still populated on the platforms our integration containers run; migrating to InitialStatus/PeerChanges is a separate change
 				resultChan <- result{&notify, nil}
 			}
 		}