tests: acpi: print error unable to dump ACPI table during rebuild

tests: acpi: print error unable to dump ACPI table during rebuild

Instead of just asserting print the error that lead to assert first.
While at it move assert into rebuild branch, which removes redundant
check done in case of !rebuild branch is taken (the later is taken
care of by g_assert_no_error).

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Wei Yang <richardw.yang@linux.intel.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <1556808723-226478-16-git-send-email-imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>