WebDAV: DNS lookup script depends on bash

syncevo-webdav-lookup.sh uses bash features (pipefail) and thus
must choose /bin/bash as shell explicitly. On systems with dash
as /bin/sh the script failed.

src/backends/webdav/syncevo-webdav-lookup.sh

@@ -1,4 +1,4 @@
-#! /bin/sh
+#! /bin/bash
 #
 # Copyright (C) 2011 Intel Corporation
 #