tap: do not close(fd) in net_init_tap_one

commit 5193e5fb (tap: factor out common tap initialization)
introduce net_init_tap_one(). But it's inappropriate that
we close fd in net_init_tap_one(), we should lay it in the
caller, becuase some callers needn't to close it if we get
the fd by monitor_handle_fd_param().

On the other hand, in other exceptional branches fd isn't
closed, so that's incomplete anyway.
Signed-off-by: NGonglei <arei.gonglei@huawei.com>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

net/tap.c

@@ -598,7 +598,6 @@ static int net_init_tap_one(const NetdevTapOptions *tap, NetClientState *peer,
 
     s = net_tap_fd_init(peer, model, name, fd, vnet_hdr);
     if (!s) {
-        close(fd);
         return -1;
     }