rpcd: update to the latest version

This update adds a couple of file plugin enhancements, such as base64 support
and setting mode when files are written.

Signed-off-by: Luka Perkov <luka@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@46384 3c298f89-4303-0410-b956-a3cf2f4a3e73