tools/libs/light: fix xl save -c handling

tools/libs/light: fix xl save -c handling

libxl_domain_resume() won't work correctly for the case it was called
due to a "xl save -c" command, i.e. to continue the suspended domain.

The information to do that is not saved in libxl__dm_resume_state for
non-HVM domains.

Fixes: 6298f0eb8f443 ("libxl: Re-introduce libxl__domain_resume")
Reported-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Tested-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Acked-by: Wei Liu <wl@xen.org>