block/nbd: connect_thread_func(): do qio_channel_set_delay(false)

block/nbd: connect_thread_func(): do qio_channel_set_delay(false)

nbd_open() does it (through nbd_establish_connection()).
Actually we lost that call on reconnect path in 1dc4718d849e1a1fe
"block/nbd: use non-blocking connect: fix vm hang on connect()"
when we have introduced reconnect thread.

Fixes: 1dc4718d849e1a1fe665ce5241ed79048cfa2cfc
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210610100802.5888-5-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>