yp_next_record() is called without a key (from xdr_my_ypresp_all()),
in which case it returns the first key in the map. When doing this,
it also needs to update the key index in the map queue entry. Without
this, ypproc_all_2_svc() (and hence ypcat) don't work correctly.
Noticed by: Michael L. Hench <hench@watt.cae.uwm.edu>
e9b8af16aa