NXCALS-1149 Fixes broken spark 2.1.1 download URL

#Merge request template @acc-logging-team - please have a look for approval.

Normally, a better practice here, should be to upgrade and opt for a newer version of spark >=2.1.2 (2.2.0 ideally), but this should be done under a dedicated task, to allocate the proper time for some checks/tests since a move will affect also the NXCALS modules (resolution to a different spark version on gradle side).

This MR comes just as a fix for the broken download link, to ensure that there'll be no impact on the current, expected functionality.

It seems, the binary sources download link was moved to the archives site, instead of the active products.

So currently we can not fetch spark binaries for the spark-scripts as stated here