MaxScale not allowing login and sometimes crashes when cache server not available

When using the new distributed cache feature on a remote host, it requires that MaxScale is able to reach that host via a network connection.

In the case of Redis, let's say the endpoint is mcsredis.nafwoo.0001.usw2.cache.amazonaws.com and the port is 6379.

However, if that endpoint and/or port is not reachable due to network outage or firewall/security rules, MaxScale becomes unresponsive and occasionally crashes.

This will likely be a blocker to a planned "Turbo" version of SkySQL in AWS.

It should probably check for connectivity and default to "in memory" or no cache during this kind of situation.