Use RFC 3986 compliant addresses in log messages

When log messages are written with both address and port information, IPv6
addresses can cause confusion if the normal address:port formatting is
used. The RFC 3986 suggests that all IPv6 addresses are expressed as a
bracket enclosed address optionally followed by the port that is separate
from the address by a colon.

In practice, the "all interfaces" address and port number 3306 can be
written in IPv4 numbers-and-dots notation as 0.0.0.0:3306 and in IPv6
notation as [::]:3306. Using the latter format in log messages keeps the
output consistent with all types of addresses.

The details of the standard can be found at the following addresses:

     https://www.ietf.org/rfc/rfc3986.txt

     https://www.rfc-editor.org/std/std66.txt

server/modules/monitor/auroramon/auroramon.c

@@ -79,7 +79,7 @@ void update_server_status(MXS_MONITOR *monitor, MXS_MONITOR_SERVERS *database)
             }
             else
             {
-                MXS_ERROR("Failed to query server %s (%s:%d): %d, %s",
+                MXS_ERROR("Failed to query server %s ([%s]:%d): %d, %s",
                           database->server->unique_name, database->server->name,
                           database->server->port, mysql_errno(database->con),
                           mysql_error(database->con));