pgsql: Fix 003_check_guc.pl when loading modules with custom GUCs

Fix 003_check_guc.pl when loading modules with custom GUCs

The test missed that custom GUCs need to be ignored from the list of
parameters that can exist in postgresql.conf.sample.  This caused the
test to fail on a server where such a module is loaded, when using
EXTRA_INSTALL and TEMP_CONFIG, for instance.

Author: Anton A. Melnikov
Discussion: https://postgr.es/m/fc5509ce-5144-4dac-8d13-21793da44fc5@postgrespro.ru
Backpatch-through: 15

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/40d5e5981cc0fa81710dc2399b063a522c36fd68

Modified Files
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src/test/modules/test_misc/t/003_check_guc.pl | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)