sysroot: Align defaults to the ospack-sysroot recipe

With this, running debos with no template parameters does not
fail badly:

    debos apertis-ospack-sysroot.yaml
    debos apertis-sysroot.yaml

Signed-off-by: Emanuele Aina <emanuele.aina@collabora.com>

apertis-sysroot.yaml

-{{ $architecture := or .architecture "armhf" }}
-{{ $ospack := or .ospack (printf "ospack-%s" $architecture) }}
+{{ $architecture := or .architecture "amd64" }}
+{{ $type := or .type "sysroot" }}
+{{ $suite := or .suite "v2019dev0" }}
+{{ $ospack := or .ospack (printf "ospack_%s-%s-%s" $suite $architecture $type) }}
 {{ $sysroot := or .sysroot (printf "sysroot-%s" $architecture) }}
 
 architecture: {{ $architecture }}