pgsql: Fix scaling of autovacuum freeze scores.

Fix scaling of autovacuum freeze scores.

Sufficiently large settings of the *_freeze_score_weight parameters
can lower the scaling thresholds below the *_freeze_max_age
settings. This can lead the scoring code to raise a value < 1.0 to
a power > 1.0, thus lowering the score, which is the opposite of
what is intended. To fix, only exponentiate the scores when doing
so won't lower their values.

Oversight in commit d7965d65fc.

Reviewed-by: Bharath Rupireddy <bharath(dot)rupireddyforpostgres(at)gmail(dot)com>
Reviewed-by: Greg Burd <greg(at)burd(dot)me>
Discussion: https://postgr.es/m/apWcbq91BAfhmsKU%40nathan
Backpatch-through: 19

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/49e098b41420aebda60804410b33fcbb5279503f

Modified Files
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src/backend/postmaster/autovacuum.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)