Ensure settings for Service and Mailer are read on the install page (#15943)

* Ensure settings for Service and Mailer are read on the install page

NewContext does not set the mailer or service settings so add
a new function that will run this.

Fix #15894

Signed-off-by: Andrew Thornton <art27@cantab.net>

* placate lint

Signed-off-by: Andrew Thornton <art27@cantab.net>

Author: zeripath

Diff for: modules/setting/setting.go

@@ -1190,3 +1190,9 @@ func NewServices() {
 	newProject()
 	newMimeTypeMap()
 }
+
+// NewServicesForInstall initializes the services for install
+func NewServicesForInstall() {
+	newService()
+	newMailService()
+}

Diff for: routers/install/setting.go

@@ -28,6 +28,7 @@ func PreloadSettings(ctx context.Context) bool {
 			log.Info("SQLite3 Supported")
 		}
 		setting.InitDBConfig()
+		setting.NewServicesForInstall()
 		svg.Init()
 	}