docker connector: refresh() delete container only if it not found but keep on failures

If inspect() call was failed due to connection problems then container will be removed anyway as like ot wasn't found.
This is probably almost never happens in real life but still some missed logic bug

connector/docker.go

@@ -160,9 +160,12 @@ func ipsFormat(networks map[string]api.ContainerNetwork) string {
 }
 
 func (cm *Docker) refresh(c *container.Container) {
-	insp := cm.inspect(c.Id)
+	insp, found, failed := cm.inspect(c.Id)
+	if failed {
+		return
+	}
 	// remove container if no longer exists
-	if insp == nil {
+	if !found {
 		cm.delByID(c.Id)
 		return
 	}
@@ -178,14 +181,17 @@ func (cm *Docker) refresh(c *container.Container) {
 	c.SetState(insp.State.Status)
 }
 
-func (cm *Docker) inspect(id string) *api.Container {
+func (cm *Docker) inspect(id string) (insp *api.Container, found bool, failed bool) {
 	c, err := cm.client.InspectContainer(id)
 	if err != nil {
-		if _, ok := err.(*api.NoSuchContainer); !ok {
+		if _, notFound := err.(*api.NoSuchContainer); notFound {
+			return c, false, false
+		}
+		// other error e.g. connection failed
 		log.Errorf("%s (%T)", err.Error(), err)
+		return c, false, true
 	}
-	}
-	return c
+	return c, true, false
 }
 
 // Mark all container IDs for refresh