cloud: Reword package doc comments for consistency

Change-Id: Ibb5f58ae944940e024edfdc0ec083cf43c331651
cloud/pubsub: Fix failing integration test for messages with nil data

Pub/Sub service seems to ignore the message published with nil data.
Testing against the case whether we can pull a nil message is obsolete.

Change-Id: I4b4632a5cb90968cecdded909b1d5fee9089f852
Merge "cloud/pubsub: Fix failing integration test for messages with nil data"