buildroot

vnstat: bump to version 1.17

Also remove patch that has been merged upstream, disable AUTORECONF
since we're no longer patching configure.ac and get rid of hack
involving the install target as the 'install-data-hook' in Makefile.am
now avoids running 'vnstat --showconfig' on the host in case of
cross-compilation.

Signed-off-by: Rodrigo Rebello <rprebello@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>