Task #8691: add basic sanity check on to activate release name to Dragnet activate script.

SubSystems/Dragnet/scripts/LOFAR-Dragnet-activate.sh

@@ -31,6 +31,15 @@ lofar_versions_root=/opt/lofar_versions
 prefix=$lofar_versions_root/$lofar_release
 nodelist="dragnet dragproc $(seq -s ' ' -f drg%02g 1 23)"
 
+# basic sanity check on selected release name
+if [ ! -e "$lofar_versions_root/$lofar_release/lofarinit.sh" ]; then
+  echo "Error: selected release is not installed: missing $lofar_versions_root/$lofar_release/lofarinit.sh"
+  exit 1
+elif [ "$lofar_release" == current ]; then
+  echo "Error: 'current' itself is not an acceptable release name to activate, as it refers to the active release"
+  exit 1
+fi
+
 # repoint 'current' symlink to release version atomically (using mv -T)
 # pray it works on every node, else the cluster's LOFAR install ends up in limbo...
 declare -a status_arr3