remote: Fix cached hypervisor type

remote: Fix cached hypervisor type

Commit 501825011c switched the remote driver to using g_auto, but missed
one case of needing to steal a pointer holding the hypervisor type.
Without it, memory is freed and the output of 'virsh version' has random
output

Compiled against library: libvirt 10.0.0
Using library: libvirt 10.0.0
Using API: ��%�U 10.0.0
Running hypervisor: ��U 8.1.3

Ths change also fixes random SIGABRT from perl processes running
libvirt-tck tests.

Signed-off-by: Jim Fehlig <jfehlig@suse.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>