feat(@angular-devkit/core): logger.log() should keep own metadata

It was possible to overwrite the metadata of the logger itself (name, path)
when calling "log()". This should not happen. If there is a need to overwrite
the loggers metadata itself one should use "next()" and construct or forward
their own log entry.

Author: hansl

packages/angular_devkit/core/src/logger/logger.ts

@@ -102,7 +102,7 @@ export class Logger extends Observable<LogEntry> implements LoggerApi {
   }
 
   log(level: LogLevel, message: string, metadata: JsonObject = {}): void {
-    const entry: LogEntry = Object.assign({}, this._metadata, metadata, {
+    const entry: LogEntry = Object.assign({}, metadata, this._metadata, {
       level, message, timestamp: +Date.now(),
     });
     this._subject.next(entry);