Curl_poll + Curl_wait_ms: fix timeout return value

Curl_poll + Curl_wait_ms: fix timeout return value

Curl_poll and Curl_wait_ms require the fix applied to Curl_socket_check
in commits b61e8b8 and c771968:

When poll or select are interrupted and coincides with the timeout
elapsing, the functions return -1 indicating an error instead of 0 for
the timeout.