treewide: parallel tests

Most tests already had no global state, however parallel was never enabled. This change enables it for all applicable tests.

Signed-off-by: Ophestra <cat@gensokyo.uk>

container/executable_test.go

@@ -9,10 +9,10 @@ import (
 )
 
 func TestExecutable(t *testing.T) {
+	t.Parallel()
 	for i := 0; i < 16; i++ {
 		if got := container.MustExecutable(message.NewMsg(nil)); got != os.Args[0] {
-			t.Errorf("MustExecutable: %q, want %q",
-				got, os.Args[0])
+			t.Errorf("MustExecutable: %q, want %q", got, os.Args[0])
 		}
 	}
 }