Fix the unexpected getaddrinfo error code changing due to parallel lookup

Parallel lookup unexpectedly changed the error code when the queries are
blocked by system.
2 problems here,
    1. the errno from query thread isn't correctly propagated to the main
thread.
    2. The rcode handling is changed.
Fix them in this CL and also add a test for this problem.

Bug: 185097438
Test: atest
Change-Id: I4c8e2895baa9d3d8ece40fe7bb8c3975672997a4