pgsql: Use library functions to edit config in SSL tests

Use library functions to edit config in SSL tests

The SSL tests were editing the postgres configuration by directly
reading and writing the files rather than using append_conf() from
the testcode library.

Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Discussion: /messages/by-id/01F4684C-8C98-4BBE-AB83-AC8D7C746AF8@yesql.se

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/ba7625a7a51b58c712541d7c0d6667c1f860e33f

Modified Files
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src/test/ssl/t/SSL/Server.pm | 81 +++++++++++++++++++++-----------------------
1 file changed, 39 insertions(+), 42 deletions(-)