Bugfix: ctr container list can not get the proper status of container

Prior to this patch, when list containers by "ctr containers" or
"ctr containers xxx", it will not get the proper status of conatinser(s).

That was caused by the wrong implementation of State() for structure process,
it only send a signal "0" to ping the "init" process and do nothing.

Since the OCI/runc has implemented an interface Status(), we can use that.
And I think this is more compatible with the design for containerd:
- containerd -> runtime -> fun()

Signed-off-by: Hu Keping <hukeping@huawei.com>

api/grpc/server/server.go

@@ -146,7 +146,11 @@ func createAPIContainer(c runtime.Container, getPids bool) (*types.Container, er
 		procs = append(procs, appendToProcs)
 	}
 	var pids []int
-	state := c.State()
+	state, err := c.Status()
+	if err != nil {
+		return nil, grpc.Errorf(codes.Internal, "get status for container: "+err.Error())
+	}
+
 	if getPids && (state == runtime.Running || state == runtime.Paused) {
 		if pids, err = c.Pids(); err != nil {
 			return nil, grpc.Errorf(codes.Internal, "get all pids for container: "+err.Error())

runtime/container_linux.go

@@ -286,7 +286,22 @@ func (c *container) Stats() (*Stat, error) {
 
 // Status implements the runtime Container interface.
 func (c *container) Status() (State, error) {
-	return "running", nil
+	args := c.runtimeArgs
+	args = append(args, "state", c.id)
+
+	out, err := exec.Command(c.runtime, args...).CombinedOutput()
+	if err != nil {
+		return "", fmt.Errorf(string(out))
+	}
+
+	// We only require the runtime json output to have a top level Status field.
+	var s struct {
+		Status State `json:"status"`
+	}
+	if err := json.Unmarshal(out, &s); err != nil {
+		return "", err
+	}
+	return s.Status, nil
 }
 
 func (c *container) OOM() (OOM, error) {