tests: possible flake in TestCopyFd about tetragon

[kkourt]

Thanks @willfindlay. I think I know what this issue is here.

We need to wait for the pipes before we call cmd.Wait()

From: https://pkg.go.dev/os/exec#Cmd.StderrPipe

It is thus incorrect to call Wait before all reads from the pipe have completed.

So something like the code below, I think. Have a bunch of other things in flight now, but will do a PR on this next.
(other tests also need to be fixed).

@@ -47,14 +47,7 @@ func TestCopyFd(t *testing.T) {
        if err != nil {
                t.Fatal(err)
        }
-
-       go func() {
-               logOut(t, "stdout> ", testPipes.StdoutRd)
-       }()
-
-       go func() {
-               logOut(t, "stderr> ", testPipes.StderrRd)
-       }()
+       defer testPipes.Close()
 
        // makeSpecFile creates a new spec file bsed on the template, and the provided arguments
        makeSpecFile := func(pid string) string {
@@ -86,6 +79,9 @@ func TestCopyFd(t *testing.T) {
                t.Fatal(err)
        }
 
+       logWG := testPipes.ParseAndLogCmdOutput(t, nil, nil)
+       logWG.Wait()
+