Mender Client log does write the default log level to syslog, no matter the configuration

If the client is run with log level lower than the default, the log output to tty is respected. However, the log written to the syslog file (/var/log/syslog, and /var/log/messages) does not respect this.

Acceptance criteria:

• Decide if we want to change this functionality or not [x]
• Implement the fix in the Mender client