We only need to check the input set for CLOSE. For all other flags we can
guarantee that the socket was included in a unique input set.

E.g. the presence of WRITE in the output flags implies that the socket must have
been in the "write" set to begin with.
Signed-off-by: Zebediah Figura <zfigura@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>