Fix docker exec command help messages
Fix docker exec command help messages

Signed-off-by: Lei Jitang <9ac444d2b5df3db1f31aa1c6462ac8e9e2bde241@huawei.com>

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