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>

test/sandbox/mount_test.go

@@ -11,6 +11,8 @@ import (
 )
 
 func TestMountinfo(t *testing.T) {
+	t.Parallel()
+
 	testCases := []struct {
 		name string
 
@@ -93,6 +95,8 @@ func TestMountinfo(t *testing.T) {
 		}
 
 		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
 			m := sandbox.NewMountinfo(name)
 			if err := m.Parse(); err != nil {
 				t.Fatalf("Parse: error = %v", err)