Do not update alert timestamp when updating a triggered alert (#10907)

* Do not update alert timestamp when updating a triggered alert

* Only update alerts timestamp if alert is triggered or recovered

* db schema

* db schema

* cleanup timestamp update

database/migrations/2019_12_05_164700_alerts_disable_on_update_current_timestamp.php

@@ -0,0 +1,28 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+
+class AlertsDisableOnUpdateCurrentTimestamp extends Migration
+{
+
+    /**
+     * Run the migrations.
+     *
+     * @return void
+     */
+    public function up()
+    {
+        \DB::statement("ALTER TABLE `alerts` CHANGE `timestamp` `timestamp` timestamp NOT NULL default CURRENT_TIMESTAMP;");
+    }
+
+    /**
+     * Reverse the migrations.
+     *
+     * @return void
+     */
+    public function down()
+    {
+        \DB::statement("ALTER TABLE `alerts` CHANGE `timestamp` `timestamp` timestamp NOT NULL default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP;");
+    }
+}