bugfix: the scheduler template (dn_schk) for the round robin scheduler
is followed by another structure (rr_schk) whose size must be set
in the schk_datalen field of the descriptor.
Not allocating the memory may cause other memory to be overwritten
(though dn_schk is 192 bytes and rr_schk only 12 so we may be lucky
and end up in the padding after the dn_schk).

This is a merge candidate for stable and 10.3

MFC after: 3 days