[script] Add unison_backup script

scripts/unison_backup.sh

@@ -0,0 +1,11 @@
+unison_exe="/usr/bin/unison"
+tmp_file=$(mktemp)
+res=$(${unison_exe} -batch > ${tmp_file} 2>&1)
+grep "Nothing to do: replicas have not changed since last sync" ${tmp_file} > /dev/null
+file_sync=$?
+
+if [ ! $file_sync == 0 ];
+then
+	echo $(more ${tmp_file})
+fi
+