Fix buildfarm failures in pg_walinspect tests.

contrib/pg_walinspect/Makefile

@@ -11,6 +11,12 @@ DATA = pg_walinspect--1.0.sql
 
 REGRESS = pg_walinspect
 
+REGRESS_OPTS = --temp-config $(top_srcdir)/contrib/pg_walinspect/walinspect.conf
+
+# Disabled because these tests require "wal_level=replica", which
+# some installcheck users do not have (e.g. buildfarm clients).
+NO_INSTALLCHECK = 1
+
 ifdef USE_PGXS
 PG_CONFIG = pg_config
 PGXS := $(shell $(PG_CONFIG) --pgxs)

contrib/pg_walinspect/expected/pg_walinspect.out

@@ -1,9 +1,13 @@
 CREATE EXTENSION pg_walinspect;
-CREATE TABLE sample_tbl(col1 int, col2 int);
 -- Make sure checkpoints don't interfere with the test.
-SELECT lsn as wal_lsn1 FROM
-  pg_create_physical_replication_slot('regress_pg_walinspect_slot', true, false)
-  \gset
+SELECT 'init' FROM pg_create_physical_replication_slot('regress_pg_walinspect_slot', true, false);
+ ?column? 
+----------
+ init
+(1 row)
+
+CREATE TABLE sample_tbl(col1 int, col2 int);
+SELECT pg_current_wal_lsn() AS wal_lsn1 \gset
 INSERT INTO sample_tbl SELECT * FROM generate_series(1, 2);
 SELECT pg_current_wal_lsn() AS wal_lsn2 \gset
 INSERT INTO sample_tbl SELECT * FROM generate_series(1, 2);

contrib/pg_walinspect/sql/pg_walinspect.sql

@@ -1,11 +1,11 @@
 CREATE EXTENSION pg_walinspect;
 
+-- Make sure checkpoints don't interfere with the test.
+SELECT 'init' FROM pg_create_physical_replication_slot('regress_pg_walinspect_slot', true, false);
+
 CREATE TABLE sample_tbl(col1 int, col2 int);
 
--- Make sure checkpoints don't interfere with the test.
-SELECT lsn as wal_lsn1 FROM
-  pg_create_physical_replication_slot('regress_pg_walinspect_slot', true, false)
-  \gset
+SELECT pg_current_wal_lsn() AS wal_lsn1 \gset
 
 INSERT INTO sample_tbl SELECT * FROM generate_series(1, 2);
 

contrib/pg_walinspect/walinspect.conf

@@ -0,0 +1,2 @@
+wal_level = replica
+max_replication_slots = 4