libguestfish.sh: actually use --ro for read-only runs
We were using `mount-ro`, but weren't passing `--ro` to guestfish
itself, so it would still try to reopen all disk images passed to it as
rw. This will fail of course if the image file is read-only.
@@ -56,6 +56,7 @@ coreos_gf_run_mount() {
if [ "$1" = ro ]; then
mntarg=mount-ro
shift
+ set -- "$@" --ro
fi
coreos_gf_run "$@"
# Detect the RHCOS LUKS case; first check if there's
