There are some architectures that support capabilities that others
do not (e.g. s390x supports cpu comparison and baseline via QEMU).

Let's make testQEMUSchemaLoad accept a string to specify the schema
to load based on the specified arch.
Signed-off-by: NCollin Walling <walling@linux.ibm.com>
Reviewed-by: NMichal Privoznik <mprivozn@redhat.com>