mysql: mysql tests should use a db server with UTC

To get rid of issues involving date/time when testing.
Also, makes it possible to run mysql integration tests for both
grafana config db and tsdb at the same time using
GRAFANA_TEST_DB=mysql go test ./pkg/...

pkg/services/sqlstore/sqlstore.go

@@ -258,7 +258,7 @@ func InitTestDB(t *testing.T) *xorm.Engine {
 	// x.ShowSQL()
 
 	if err != nil {
-		t.Fatalf("Failed to init in memory sqllite3 db %v", err)
+		t.Fatalf("Failed to init test database: %v", err)
 	}
 
 	sqlutil.CleanDB(x)
@@ -269,3 +269,12 @@ func InitTestDB(t *testing.T) *xorm.Engine {
 
 	return x
 }
+
+func IsTestDbMySql() bool {
+	if db, present := os.LookupEnv("GRAFANA_TEST_DB"); present {
+		return db == dbMySql
+	}
+
+	return false
+}
+