test: Fix AdapterGroongaSelectTest

This patch makes 7 tests to be green, however, I'm not sure about this change. This is why I'm sending this PR. Could anyone confirm this patch?

```
 ./test/run-test.rb --testcase /AdapterGroongaSelectTest/       
(snip)
7 tests, 7 assertions, 7 failures, 0 errors, 0 pendings, 0 omissions, 0 notifications
0% passed
```

to 

```
 ./test/run-test.rb --testcase /AdapterGroongaSelectTest/       
(snip)
7 tests, 7 assertions, 0 failures, 0 errors, 0 pendings, 0 omissions, 0 notifications
100% passed

```

According to bisect, 339f6342db06eb8f333be2ef4cddea2ac26d8e9a is the first commit that makes these tests red.