title: Angular ngx-translate getTranslation issue
body: <p>I am using ngx-translate to translate my Angular Web-app, and it seems that ngx-translate has an issue with the function <code>getTranslation(language)</code>. When it's called, it changes the current language ?temporarly? and then my component is not displayed in the right language.</p>
  
  <pre><code>export class InputRadioComponent extends FormComponentInput implements OnInit {
    constructor(protected formDynamicS) {
    }
  
    public ngOnInit() {
      this.translate.getTranslation("fr").subscribe(res =&gt; {
        this.choose["fr"] = res['form-component']['choose-answer'];
      });
      this.translate.getTranslation("en").subscribe(res =&gt; {
        this.choose["en"] = res['form-component']['choose-answer'];
      });
      this.translate.getTranslation("de").subscribe(res =&gt; {
        this.choose["de"] = res['form-component']['choose-answer'];
      });
    }
  }
  </code></pre>
  
  <p>In this case, like <code>this.translate.getTranslation("de")</code> is the last call, my component is always displayed in german. I find a workaround but it's not something I want to keep on my code. Here is my workaround :</p>
  
  <pre><code>let languages: string[] = ["fr", "en", "de"];
  
  languages.splice(languages.indexOf(this.translate.currentLang));
  languages.push(this.translate.currentLang);
  
  languages.forEach((language) =&gt; {
    this.translate.getTranslation(language).subscribe(res =&gt; {
      this.choose[language] = res['form-component']['choose-answer'];
    });
  });
  </code></pre>
  
  <p>It allows me to keep the currentLang, because it will be the last call by <code>getTranslation</code></p>