pgsql: Fix lastReplayedEndRecPtr calculation when starting from shutdow

Fix lastReplayedEndRecPtr calculation when starting from shutdown checkpoint.

When entering crash recovery followed by archive recovery, and the latest
checkpoint is a shutdown checkpoint, and there are no more WAL records to
replay before transitioning from crash to archive recovery, we would not
immediately allow read-only connections in hot standby mode even if we
could. That's because when starting from a shutdown checkpoint, we set
lastReplayedEndRecPtr incorrectly to the record before the checkpoint
record, instead of the checkpoint record itself. We don't run the redo
routine of the shutdown checkpoint record, but starting recovery from it
goes through the same motions, so it should be considered as replayed.

Reported by Kyotaro HORIGUCHI. All versions with hot standby are affected,
so backpatch to 9.0.

Branch
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REL9_3_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/2cd72ba42d22a1d19cfb9c01e59f82519ab22a9f

Modified Files
--------------
src/backend/access/transam/xlog.c |   12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)