Refactoring PluginManager to be a self registering service (#11755)

* refator: refactored PluginManager to be a self registering service, a lot more work needed to fully make plugin manager use instance variables and not so many globals

pkg/plugins/update_checker.go

@@ -26,23 +26,6 @@ type GithubLatest struct {
 	Testing string `json:"testing"`
 }
 
-func StartPluginUpdateChecker() {
-	if !setting.CheckForUpdates {
-		return
-	}
-
-	// do one check directly
-	go checkForUpdates()
-
-	ticker := time.NewTicker(time.Minute * 10)
-	for {
-		select {
-		case <-ticker.C:
-			checkForUpdates()
-		}
-	}
-}
-
 func getAllExternalPluginSlugs() string {
 	var result []string
 	for _, plug := range Plugins {
@@ -56,8 +39,12 @@ func getAllExternalPluginSlugs() string {
 	return strings.Join(result, ",")
 }
 
-func checkForUpdates() {
-	log.Trace("Checking for updates")
+func (pm *PluginManager) checkForUpdates() {
+	if !setting.CheckForUpdates {
+		return
+	}
+
+	pm.log.Debug("Checking for updates")
 
 	pluginSlugs := getAllExternalPluginSlugs()
 	resp, err := httpClient.Get("https://grafana.com/api/plugins/versioncheck?slugIn=" + pluginSlugs + "&grafanaVersion=" + setting.BuildVersion)