If the socket timeout is 0 then a failed socket.connect() raises
EINPROGRESS (which is what the lwIP bindings already did), but if the
socket timeout is non-zero then a failed socket.connect() should raise
ETIMEDOUT. The latter is fixed in this commit.
A test is added for these timeout cases.
Signed-off-by: Damien George <damien@micropython.org>
