ws2_32_apitest:send CANCELED in r68120 and onwards

The test just hangs. There are two issues here:

• send on a disconnected socket should fail with WSAENOTCONN, instead afd just queues the request and waits forever
• with the first problem fixed, a sendto with length 0 asserts when afd calls IoAllocateMdl on the buffer. This case needs to be handled specifically by simply returning success