anaconda in F34 and Rawhide recently stopped accepting params
without the inst. prefix, so 'rescue' does nothing except print
a warning now. We need to use `inst.rescue`. This has worked for
quite a long time so will be OK at least on all Fedoras and RHEL
8, not sure about RHEL 7.
Signed-off-by: Adam Williamson <awilliam@redhat.com>