Improve pre error handling

ROOT/usr/lib/chem-zfs-backup-server/zfs-rsync.sh

@@ -34,6 +34,13 @@ fi
 # Prepare the host if required
 if [ ! -z "$PRE" ] ; then
  $PRE $HN >>$LOGDIR/${HN}_${TAG}-pre.log 2>&1
+
+ PRE_EXIT=$?
+ if [ $PRE_EXIT -ne 0 ] ; then
+   echo PRE script $PRE exited with $PRE_EXIT >>$LOGFILE
+   exit $PRE_EXIT
+ fi
+
 fi
 
 # Do the backup