MM-18741: clarify error message (#12357)

Clarify the error message that is emitted by the server when failing to parse the configuration.

Fixes: MM-18741

cmd/mattermost/commands/server.go

@@ -47,7 +47,7 @@ func serverCmdF(command *cobra.Command, args []string) error {
 	}
 	configStore, err := config.NewStore(configDSN, !disableConfigWatch)
 	if err != nil {
-		return err
+		return errors.Wrap(err, "failed to load configuration")
 	}
 
 	return runServer(configStore, disableConfigWatch, usedPlatform, interruptChan)