Implemet docker update command

It's used for updating properties of one or more containers, we only
support resource configs for now. It can be extended in the future.

Signed-off-by: Qiang Huang <h.huangqiang@huawei.com>

common.go

@@ -64,6 +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"},
 	{"version", "Show the Docker version information"},
 	{"volume", "Manage Docker volumes"},
 	{"wait", "Block until a container stops, then print its exit code"},