pgsql: Fix WAL replay of locking an updated tuple

Fix WAL replay of locking an updated tuple

We were resetting the tuple's HEAP_HOT_UPDATED flag as well as t_ctid on
WAL replay of a tuple-lock operation, which is incorrect when the tuple
is already updated.

Back-patch to 9.3. The clearing of both header elements was there
previously, but since no update could be present on a tuple that was
being locked, it was harmless.

Bug reported by Peter Geoghegan and Greg Stark in
CAM3SWZTMQiCi5PV5OWHb+bYkUcnCk=O67w0cSswPvV7XfUcU5g(at)mail(dot)gmail(dot)com and
CAM-w4HPTOeMT4KP0OJK+mGgzgcTOtLRTvFZyvD0O4aH-7dxo3Q(at)mail(dot)gmail(dot)com
respectively; diagnosis by Andres Freund.

Branch
------
REL9_3_STABLE

Details
-------
http://git.postgresql.org/pg/commitdiff/9a57858f1103b89a5674f0d50c5fe1f756411df6

Modified Files
--------------
src/backend/access/heap/heapam.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)