Adjust Kafka tests to tolerate slow consumer startup

As part of validating 1.2.0 I ran samples/connectors/kafka.

Manually running of the kafka tests didn't initially succeed due to consumer startup being very slow (10sec?) this time on my Mac for some reason (running local zookeeper & kafka server).
Adjust both the test's PUB_DELAY_MSEC (15s) and SEC_TIMEOUT (40s) was required to make them pass.

I'm pretty sure this has nothing to do with the connector/Edgent (but will check more).

The tests should be changed so as to tolerate this sort of condition if possible e.g., instead of using a fixed initial delay for publishing, there should be some "gate" that blocks tuple publishing until the subscriber is connected.