Disregard this one for now. If o_get returns -1 it indicates an error,
so it should indicate this to the upper layers. However, the old code
can't handle this and I kept this code as is so that we can have some
time to let the dust settle around the new code (and easily switch back
if needed).
When hitting an error case in mps_get{,next}req, mps assumes that no OID
has been linked to the root element. However, in both the get as well as
the getnext case it's already set when entering the mib.c code, so going
the fail goto path will result in the intended OID/exception pair being
