s390: qemu-capabilities: Avoid error message when missing non-kvm host cpu info

s390: qemu-capabilities: Avoid error message when missing non-kvm host cpu info

Libvirt prints an error on startup when it is missing host cpu model
information for any queried qemu binary. On s390 we only have host cpu model
information for kvm enabled qemu instances. So when virt type is not kvm, this
is actually not an error on s390.

This patch adds virt type as a parameter to virQEMUCapsInitCPUModelS390, and a
new return code 2 for virQEMUCapsInitCPUModel and virQEMUCapsInitCPUModelS390.
If the virt type is not kvm then we skip printing the scary error message
and return 2 because this case is actually expected behavior. The new return
code is meant to differentiate between the failure case and the case where we
simply expect the cpu model information to be unattainable.

Signed-off-by: Jason J. Herne <jjherne@linux.vnet.ibm.com>
Reviewed-by: Boris Fiuczynski <fiuczy@linux.vnet.ibm.com>
Reviewed-by: Marc Hartmayer <mhartmay@linux.vnet.ibm.com>
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>