When executed with --dry-run, repmgr outputs detail about what would
happen using log level INFO. If the log_level is configured to
NOTICE or higher, it's possible some or all of the --dry-run output
might not be displayed.
Addresses GitHub #441.
This is more consistent with other parameters and conforms to
the pattern used by PostgreSQL itself, which uses the prefix "log_"
for logging parameters.
A warning will be emitted if the old version of the parameter name
is detected.