Altere o nível de log usado no seu arquivo NetworkManager.conf
[logging] This section controls NetworkManager's logging. Any settings here are overridden by the --log-level and --log-domains command-line options.
level=<level> One of [ERR, WARN, INFO, DEBUG]. The ERR level logs only critical errors. WARN logs warnings that may reflect operation. INFO logs various informational messages that are useful for tracking state and operations. DEBUG enables verbose logging for debugging purposes. Subsequent levels also log all messages from earlier levels; thus setting the log level to INFO also logs error and warning messages.
Mas observe esta parte:
This section controls NetworkManager's logging. Any settings here are overridden by the --log-level and --log-domains command-line options.