Update xtrabackup scripts

* Add pissibility to pass force-non-empty-directories option
* Follow symlinks for find

Related-Prod: PROD-36049
Change-Id: If3638ef66528a995549befac4a22f3ffd4a84be4
diff --git a/README.rst b/README.rst
index d4137ff..6b04064 100644
--- a/README.rst
+++ b/README.rst
@@ -254,6 +254,7 @@
         compression: true
         rsync_tables: true
         compressThreads: 2
+        force_non_empty_directories: true
         database:
           user: username
           password: password