pgsql: Fix autovacuum cost debug logging

Fix autovacuum cost debug logging

Commit 7d71d3dd0 introduced finer grained updates of autovacuum option
changes by increasing the frequency of reading the configuration file.
The debug logging of cost parameter was however changed such that some
initial values weren't logged.  Fix by changing logging to use the old
frequency of logging regardless of them changing.

Also avoid taking a log for rendering the log message unless the set
loglevel is such that the log entry will be emitted.

Author: Masahiko Sawada <sawada.mshk@gmail.com>
Discussion: https://postgr.es/m/CAD21AoBS7o6Ljt_vfqPQPf67AhzKu3fR0iqk8B=vVYczMugKMQ@mail.gmail.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/a9781ae11ba2fdb44a3a72c9a7ebb727140b25c5

Modified Files
--------------
src/backend/postmaster/autovacuum.c | 15 +++++----------
1 file changed, 5 insertions(+), 10 deletions(-)