Data Processing: Fixing UI refresh for deleted clusters

An Http404 is now returned when an update request comes
in for a cluster that has been deleted which will trigger
the appropriate UI update (removal of that cluster).

Change-Id: I7216d361d3d09cb593b6ca2f3b89bfb9fc67917e
Closes-Bug:  bug #1336292
Co-Authored-By: Andrew Lazarev <alazarev@mirantis.com>
Merge "Data Processing: Fixing UI refresh for deleted clusters"