rules: Fix handling of ARCHES_{QEMU,LXC}

Some contents, notably configuration files, are only installed
by the upstream build system when the corresponding driver has
been enabled.

Most of these changes are quite self-explanatory, but the
test_libvirt_lockd and test_libvirt_sanlock augeas lenses
stand out. Despite the name not suggesting that, they're
actually testing the qemu-lockd.conf and qemu-sanlock.conf
files, so they are only installed if the QEMU driver has been
enabled.