all: fix golangci-lint errors

These erroneously blocked a recent PR, which I fixed by simply
re-running CI. But we might as well fix them anyway.
These are mostly `printf` to `print` and a couple of `!=` to `!Equal()`

Updates #cleanup

Signed-off-by: Will Norris <will@tailscale.com>

tstest/integration/testcontrol/testcontrol.go

@@ -955,7 +955,7 @@ func (s *Server) MapResponse(req *tailcfg.MapRequest) (res *tailcfg.MapResponse,
 	if dns != nil && s.MagicDNSDomain != "" {
 		dns = dns.Clone()
 		dns.CertDomains = []string{
-			fmt.Sprintf(node.Hostinfo.Hostname() + "." + s.MagicDNSDomain),
+			node.Hostinfo.Hostname() + "." + s.MagicDNSDomain,
 		}
 	}