MB-7476: Prepend bucket name to all log messages

Change-Id: I1053494b5359c702c25e4bffa7e88959cb87be53
Reviewed-on: http://review.couchbase.org/24249
Reviewed-by: Chiyoung Seo <chiyoung.seo@gmail.com>
Tested-by: Chiyoung Seo <chiyoung.seo@gmail.com>