daemon.md: fix placement of exec driver heading
daemon.md: fix placement of exec driver heading

Options for zfs storage driver were incorrectly placed
under 'exec driver options' header. Move the header to
the correct place.

Signed-off-by: Kir Kolyshkin <c0159612b0ef32139322233232df1a0d189c4b9b@openvz.org>

docker/cli,e11137/cli,cpuguy83/cli,cpuguy83/cli,redpanda/cli,docker/cli,dnephin/cli,riyazdf/cli,e11137/cli,ashfall/cli,thaJeztah/cli,Zebrilee/cli,ashfall/cli,Zebrilee/cli,riyazdf/cli,redpanda/cli,dnephin/cli,thaJeztah/cli,allencloud/cli,allencloud/cli