The fix in Spring Data Redis for sentinel configuration means that
two Jedis sentinel tests now attempt to connect to a Sentinel. As a
result the tests fail. Running a Redis Sentinel in a Docker container
appears to be non-trivial. As an alternative, this commit updates the
tests to capture the JedisConnectionFactory prior to its
initialization (which is the failure trigger) and then assert that its
configuration is as expected.

See gh-11884
Closes gh-11855