Stop PdfToHtmlWorker if pdfconverter failed to create a job

When creating a job for pdfconverter response status code should be 201. 
Currently, that is not checked and in case pdfconverter service fail to create a job for some reason worker still tries to retrieve converted HTML, which won't be possible.

Solution:

Add checking status code after creating a job for pdfconverter and throw an error if it is not 201