Fix db init log and log format issue

src/nni_manager/common/log.ts

@@ -138,7 +138,7 @@ class Logger {
     private log(level: string, param: any[]): void {
         const buffer: WritableStreamBuffer = new WritableStreamBuffer();
         buffer.write(`[${(new Date()).toISOString()}] ${level} `);
-        buffer.write(format(null, param));
+        buffer.write(format(param));
         buffer.write('\n');
         buffer.end();
         this.bufferSerialEmitter.feed(buffer.getContents());

src/nni_manager/core/nniDataStore.ts

@@ -49,6 +49,7 @@ class NNIDataStore implements DataStore {
         if(isNewExperiment()) {
             mkDirP(databaseDir).then(() => {
                 this.db.init(true, databaseDir).then(() => {
+                    this.log.info('Datastore initialization done');
                     this.initTask.resolve();
                 }).catch((err: Error) => {
                     this.initTask.reject(err);
@@ -58,6 +59,7 @@ class NNIDataStore implements DataStore {
             });
         } else {
             this.db.init(false, databaseDir).then(() => {
+                this.log.info('Datastore initialization done');
                 this.initTask.resolve();
             }).catch((err: Error) => {
                 this.initTask.reject(err);

src/nni_manager/rest_server/restHandler.ts

@@ -115,7 +115,6 @@ class NNIRestHandler {
             const ds: DataStore = component.get<DataStore>(DataStore);
             ds.init().then(() => {
                 res.send(this.nniManager.getStatus());
-                this.log.info('Datastore initialization done');
             }).catch(async (err: Error) => {
                 this.handle_error(err, res);
                 this.log.error(err.message);