Qemu always opens the tray if forced to. Skip the waiting step in such
case.

This also helps if qemu does not report the tray change event when
opening the cdrom forcibly (the documentation says that the event will
not be sent although qemu in fact does trigger it even if @force is
selceted).

This is a workaround for a qemu issue where qemu does not send the tray
change event in some cases (after migration with empty closed locked
drive) and thus renders the cdrom useless from libvirt's point of view.

Partially resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1368368