connection_keepalive and error : (4852) Unexpected internal state: received response 0x00 from server

We saw the following error logged in MaxScale 2.3.3:

error : (4852) Unexpected internal state: received response 0x00 from server 'mariadb-server' when no response was expected. Command: 0x03 Query: <not available>

As I understand it, this should not have any negative side effects, but it seems to indicate a problem with the connection_keepalive ping mechanism.

A potential work-around/solution to avoid this to set the value of `connection_timeout` to a value close to `wait_timeout` to hopefully reduce the chance of logging these warnings.