lib/file/apb_open: combine apb and abb opens
lib/file/apb_open: combine apb and abb opens

Use a common open function to reduce duplication for mgmt / io conn
split.

Signed-off-by: David Disseldorp <589a549dc9f982d9f46aeeb82a09ab6d87ccf1d8@suse.de>

ddiss/elasto,ddiss/elasto