pgsql: Choose ports for test servers less likely to result in conflicts

Choose ports for test servers less likely to result in conflicts

If we choose ports in the range typically used for ephemeral ports there
is a danger of encountering a port conflict due to a race condition
between the time we choose the port in a range below that typically used
to allocate ephemeral ports, but higher than the range typically used by
well known services.

Author: Jelte Fenema-Nio, with some editing by me.

Discussion: https://postgr.es/m/d6ee8761-39d1-0033-1afb-d5a57ee056f2@gmail.com

Backpatch to all live branches (12 and up)

Branch
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REL_15_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/33470429f2bdb967d945b72a5b553fbc6d1d8f96

Modified Files
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src/test/perl/PostgreSQL/Test/Cluster.pm | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)