readline: fixes scoping bug

Signed-off-by: Fedor Indutny <fedor@indutny.com>
net: don't throw on net.Server.close()

When close() is called on a non-listening server, a synchronous
error is thrown. This commit causes the error to be passed to
the asynchronous callback function instead.

Signed-off-by: Fedor Indutny <fedor@indutny.com>