MB-31517 MB-31515 Correct cbbackup accu behaviour
MB-31517 MB-31515 Correct cbbackup accu behaviour

Accumulative backups where creating full backups after the first
accumulative backup. This has been fixed and now when making
accumulative backups if it is the first backup it will create a full
backup. The second time it will store new elements since the last full
and the next time it will again store all the new elements since the
last full. The differential backups will store every new element since
the last backup regardless of what type of backup it is.

Change-Id: If8c60902e4aa489be806910253caf5ebab6cf5a3
Reviewed-on: http://review.couchbase.org/102256
Tested-by: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Patrick Varley <cbb7353e6d953ef360baf960c122346276c6e320@couchbase.com>

couchbase/couchbase-cli,couchbase/couchbase-cli