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 <kir@openvz.org>

docs/reference/commandline/daemon.md

@@ -323,9 +323,6 @@ options for `zfs` start with `zfs`.
 
         $ docker -d --storage-opt dm.blkdiscard=false
 
-
-## Docker execdriver option
-
 Currently supported options of `zfs`:
 
  * `zfs.fsname`
@@ -338,6 +335,8 @@ Currently supported options of `zfs`:
 
         $ docker -d -s zfs --storage-opt zfs.fsname=zroot/docker
 
+## Docker execdriver option
+
 The Docker daemon uses a specifically built `libcontainer` execution driver as
 its interface to the Linux kernel `namespaces`, `cgroups`, and `SELinux`.