package_manager.py: Reverse rpm arch order

package_manager.py: Reverse rpm arch order

The architecture list used by dnf/libsolv was in the wrong order.
As a result, the images were built with wrong and unpredictable
packages.

$ MACHINE=intel-corei7-64 bitbake core-image-sato
$ MACHINE=qemux86-64 bitbake core-image-sato
$ MACHINE=intel-corei7-64 bitbake -ccleansstate core-image-sato
$ MACHINE=intel-corei7-64 bitbake core-image-sato

The first image had 0 core2_64 packages in it, but the last one had
583 core2_64 packages (which were built for the qemu image in
between).

Reverse the arch order in etc/dnf/vars/arch.

Fixes [YOCTO #11384].

Signed-off-by: Jussi Kukkonen <jussi.kukkonen@intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>