MXS-1819 Also log info messages to syslog

If info messages are enabled, they will be logged to syslog
just like any other messages.

Documentation/Getting-Started/Configuration-Guide.md

@@ -261,9 +261,10 @@ not regularly.
 Since *MariaDB MaxScale* can log to both file and *syslog* an approach that
 provides maximum flexibility is to enable *syslog* and *log_to_shm*, and to
 disable *maxlog*. That way messages will normally be logged to *syslog*, but if
-there is something to investigate, *log_info* and *maxlog* can be enabled from
+there is something to investigate, *log_debug* and *maxlog* can be enabled from
 *maxadmin*, in which case informational messages will be logged to the
-*maxscale.log* file that resides in shared memory.
+*maxscale.log* file that resides in shared memory. But note that *log_debug*
+messages will only be available if MaxScale has been built in debug mode.
 
 By default, logging to shared memory is disabled.
 

server/core/log_manager.cc

@@ -895,11 +895,12 @@ static int logmanager_write_log(int            priority,
         case LOG_ERR:
         case LOG_WARNING:
         case LOG_NOTICE:
+        case LOG_INFO:
             syslog(priority, "%s", message);
             break;
 
         default:
-            // LOG_INFO and LOG_DEBUG messages are never written to syslog.
+            // LOG_DEBUG messages are never written to syslog.
             break;
         }
     }