test/timeout: Fix `-Werror=maybe-uninitialized`

Fix this:
```
  timeout.c: In function ‘test_multi_timeout’:
  timeout.c:590:20: warning: ‘user_data’ may be used uninitialized in this function [-Wmaybe-uninitialized]
    590 |                 if (cqe->user_data != user_data) {
        |                    ^
  timeout.c:601:51: warning: ‘time’ may be used uninitialized in this function [-Wmaybe-uninitialized]
    601 |                 if (exp < time / 2 || exp > (time * 3) / 2) {
        |                                             ~~~~~~^~~~
```

Fixes: 37136cb4

 ("test/timeout: add multi timeout reqs test with different timeout")
Cc: zhangyi (F) <yi.zhang@huawei.com>
Signed-off-by: Ammar Faizi <ammar.faizi@students.amikom.ac.id>
Link: https://lore.kernel.org/r/hgUsvvrR9xY-ammarfaizi2@gnuweeb.org


Signed-off-by: Jens Axboe <axboe@kernel.dk>