pgsql: Make SSL tests more robust

Make SSL tests more robust

Someone running these test could have key or certificate files in
their ~/.postgresql/, which would interfere with the tests. The way
to override that is to specify sslcert=invalid and/or
sslrootcert=invalid if no actual certificate is used for a particular
test. Document that and fix up one test that had a risk of failing in
these circumstances.

Discussion: /messages/by-id/398754d8-6bb5-c5cf-e7b8-22e5f0983caf@2ndquadrant.com/

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/bdd6e9ba171765ae34d320e1be17717620cb491c

Modified Files
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src/test/ssl/ServerSetup.pm | 10 ++++++++++
src/test/ssl/t/002_scram.pl | 2 +-
2 files changed, 11 insertions(+), 1 deletion(-)