Initialize return code to 0

If there is a handle in the wait list, but there is not an event,
_hlist_do_poll_locked will return an uninitialized ret variable.

This patch sets the default return code to 0, for no event.

Bug: 140626835
Change-Id: Ib42160c8456b880b3253533a0a7266a180b36d34
1 file changed