pgsql: Adjust weird usages of sentinel_ok()

Adjust weird usages of sentinel_ok()

All other callers of sentinel_ok() pass the palloc'd address to the
function and the requested size of the allocation as the 2nd parameter.
Here we adjust 3 locations that were passing the MemoryChunk and adding on
sizeof(MemoryChunk) onto the byte count. Effectively, it's the same byte,
but a strange way to calculate it.

Author: David Rowley <dgrowleyml(at)gmail(dot)com>
Reviewed-by: shihao zhong <zhong950419(at)gmail(dot)com>
Discussion: https://postgr.es/m/CAApHDvq7HyLWX27XCSf5BmijeObV-QUF6CCbKAW00LxFPc71Ag@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/57926d757ab43852021d917b6221687a341c8385

Modified Files
--------------
src/backend/utils/mmgr/aset.c | 2 +-
src/backend/utils/mmgr/generation.c | 2 +-
src/backend/utils/mmgr/slab.c | 2 +-
3 files changed, 3 insertions(+), 3 deletions(-)