[pgpool-committers: 9431] pgpool: Fix delay_threshold_by_time and prefer_lower_standby_delay.

[Tatsuo Ishii]

Fix delay_threshold_by_time and prefer_lower_standby_delay.

They were broken since delay_threshold_by_time was introduced in 4.4.

- delay_threshold_by_time was not checked in where_to_send. This broke
  load balancing when replication is delayed.

- select_load_balancing_node was broken if both
  delay_threshold_by_time and prefer_lower_standby_delay were enabled.

In order to fix the issue, where_to_send and
select_load_balancing_node are fixed.  Also add test case for
delay_threshold_by_time are added to 033.prefer_lower_standby_delay.

Discussion: https://www.pgpool.net/pipermail/pgpool-general/2023-June/008864.html

Branch
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V4_4_STABLE

Details
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https://git.postgresql.org/gitweb?p=pgpool2.git;a=commitdiff;h=6aebf24aa9a627f4c852e44f6407f17a34d50528

Modified Files
--------------
src/context/pool_query_context.c                   |   7 +-
src/protocol/pool_pg_utils.c                       |  31 ++--
.../tests/033.prefer_lower_standby_delay/test.sh   | 183 ++++++++++++++++-----
3 files changed, 163 insertions(+), 58 deletions(-)