Replace docker command from 'docker daemon' to 'dockerd'

Signed-off-by: yuexiao-wang <wang.yuexiao@zte.com.cn>
Upstream-commit: 530668cb2262fc89e60a23d9a0f6555498b0171b
Component: engine

components/engine/docs/reference/commandline/dockerd.md

@@ -574,7 +574,7 @@ options for `zfs` start with `zfs` and options for `btrfs` start with `btrfs`.
     **size** cannot be smaller than **btrfs.min_space**.
 
     Example use:
-        $ docker daemon -s btrfs --storage-opt btrfs.min_space=10G
+        $ dockerd -s btrfs --storage-opt btrfs.min_space=10G
 
 #### Overlay2 options
 
@@ -1213,7 +1213,7 @@ The `--tls*` options enable use of specific certificates for individual daemons.
 Example script for a separate “bootstrap” instance of the Docker daemon without network:
 
 ```bash
-$ docker daemon \
+$ dockerd \
         -H unix:///var/run/docker-bootstrap.sock \
         -p /var/run/docker-bootstrap.pid \
         --iptables=false \