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/stub/call_test.go

@@ -8,13 +8,17 @@ import (
 )
 
 func TestCallError(t *testing.T) {
+	t.Parallel()
+
 	t.Run("contains false", func(t *testing.T) {
+		t.Parallel()
 		if err := new(stub.Call).Error(true, false, true); !reflect.DeepEqual(err, stub.ErrCheck) {
 			t.Errorf("Error: %#v, want %#v", err, stub.ErrCheck)
 		}
 	})
 
 	t.Run("passthrough", func(t *testing.T) {
+		t.Parallel()
 		wantErr := stub.UniqueError(0xbabe)
 		if err := (&stub.Call{Err: wantErr}).Error(true); !reflect.DeepEqual(err, wantErr) {
 			t.Errorf("Error: %#v, want %#v", err, wantErr)