Denser partition version logging

The logging of the partition versions when the group header was
updated was spread across several lines. That is neither useful
when skipping over the logs, nor when grepping in the logs. Hence
put the partition versions output into a single line.

Change-Id: I19f4872c4c063b54385d86ad1258110a8a6e04d2
Reviewed-on: http://review.couchbase.org/39206
Reviewed-by: Volker Mische <volker.mische@gmail.com>
Tested-by: Volker Mische <volker.mische@gmail.com>
Reviewed-by: Sarath Lakshman <sarath@couchbase.com>