Update RestartPolicy of container

Add `--restart` flag for `update` command, so we can change restart
policy for a container no matter it's running or stopped.

Signed-off-by: Zhang Wei <zhangwei555@huawei.com>

common.go

@@ -64,7 +64,7 @@ var dockerCommands = []Command{
 	{"tag", "Tag an image into a repository"},
 	{"top", "Display the running processes of a container"},
 	{"unpause", "Unpause all processes within a container"},
-	{"update", "Update resources of one or more containers"},
+	{"update", "Update configuration of one or more containers"},
 	{"version", "Show the Docker version information"},
 	{"volume", "Manage Docker volumes"},
 	{"wait", "Block until a container stops, then print its exit code"},