dsnap-sync: adopt standard snapper location hosting the configs

Signed-off-by: Ralf Zerres <ralf.zerres@networkx.de>

find_snapper_config

@@ -0,0 +1,15 @@
+#!/bin/sh
+
+etcdirs="sysconfig default conf.d"
+
+for x in $etcdirs; do
+    d=/etc/$x/snapper
+    if [ -f $d ]; then
+	    sed -i 's@^SNAPPER_CONFIG=.*@SNAPPER_CONFIG='$d'@g' bin/dsnap-sync
+        exit 0
+    fi
+done
+
+printf "==> Unable to find snapper configuration file in a standard location.\n"
+printf "==> Using SNAPPER_CONFIG make variable.\n"
+exit 1