Improve the logging in KafkaRoller class

The KafkaRoller class seems to log most of its messages on the DEBUG level. That is seemingly ok if everything works as expected and there are no delays. But in case of issues such as ENTMQST-1556 it might get stuck for possibly long time in some timeouts. All this time there is no message printed on the INFO level or above, so the user does not know what is going on.

We need to improve the logging here to tell the user what are we trying to do and possibly inform them about the errors, backoffs etc.

This JIRA was created by Strimzi#2264