refactor: log lockfileUpdate

lib/manager/npm/post-update/npm.js

@@ -79,6 +79,7 @@ async function generateLockFile(
     logger.debug(`npm stderr:\n${stderr}`);
     const lockUpdates = upgrades.filter(upgrade => upgrade.isLockfileUpdate);
     if (lockUpdates.length) {
+      logger.info('Performing lockfileUpdate (npm)');
       const updateCmd =
         cmd +
         lockUpdates

lib/manager/npm/post-update/yarn.js

@@ -93,6 +93,7 @@ async function generateLockFile(cwd, env, config = {}, upgrades = []) {
       .filter(upgrade => upgrade.isLockfileUpdate)
       .map(upgrade => upgrade.depName);
     if (lockUpdates.length) {
+      logger.info('Performing lockfileUpdate (yarn)');
       const updateCmd =
         cmd +
         ' upgrade' +