iotests/041: Fix NBD socket path

We should put all UNIX socket files into the sock_dir, not test_dir.

Reported-by: Elena Ufimtseva <elena.ufimtseva@oracle.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200424134626.78945-1-mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Fixes: a1da187
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>

tests/qemu-iotests/041

@@ -35,7 +35,7 @@ quorum_img3 = os.path.join(iotests.test_dir, 'quorum3.img')
 quorum_repair_img = os.path.join(iotests.test_dir, 'quorum_repair.img')
 quorum_snapshot_file = os.path.join(iotests.test_dir, 'quorum_snapshot.img')
 
-nbd_sock_path = os.path.join(iotests.test_dir, 'nbd.sock')
+nbd_sock_path = os.path.join(iotests.sock_dir, 'nbd.sock')
 
 class TestSingleDrive(iotests.QMPTestCase):
     image_len = 1 * 1024 * 1024 # MB