BibTasklets: webcoll tasklet improvements

* Improves the the webcoll robotupload tasklet on several levels:

* Adds connection to redis to keep any recids pending if the
  request should fail.

* Fixes an issue with passing arguments to the tasklet.

* Now warns if the config variable CFG_WEBCOLL_POST_REQUEST_URL is not
  set.

Signed-off-by: Jan Aage Lavik <jan.age.lavik@cern.ch>