Periodic tasks refactor (#62)

* Once every second the session run a list of periodic tasks on every
instance concurrently. We use these tasks to do things like:
- Collect mem and cpu stats
- Check if instance is part of a swarm cluster
- Broadcast information to connected clients

services/check_swarm_status_task.go

@@ -0,0 +1,15 @@
+package services
+
+import "github.com/docker/docker/api/types/swarm"
+
+type checkSwarmStatusTask struct {
+}
+
+func (c checkSwarmStatusTask) Run(i *Instance) {
+	if info, err := GetDaemonInfo(i); err == nil {
+		if info.Swarm.LocalNodeState != swarm.LocalNodeStateInactive && info.Swarm.LocalNodeState != swarm.LocalNodeStateLocked {
+			i.IsManager = &info.Swarm.ControlAvailable
+		}
+	}
+
+}