Fix busy loop in various IO functions on some platforms

Don't include STREAM_AWAIT_ERROR in stream_await call

Summary:
STREAM_AWAIT_ERROR is a return code, not an event type.

This is fine on some Linux systems, but on others and MacOS it returns instantly, leading to busy loops.

This API isn't as typed as we'd like as it's older than enums. Being replaced
with HSL IO.

Reviewed By: alexeyt

Differential Revision: D14142241

fbshipit-source-id: d5f9be7b5e68893fde113473c6a5d9adf2394abf