Add a description in the usage text

Author: jcharaoui

resources/ext/cli/prune-reports.erb

@@ -1,6 +1,8 @@
 #!/usr/bin/env bash
 
 usage() {
+    echo "Delete old reports stored in 'reportdir' ($(puppet config print reportdir))."
+    echo
     echo "Usage: puppetserver prune-reports [<ttl>]"
     echo "  <ttl>         delete reports older than this amount of time (default: 14d)"
     exit 0