missing data - vbucketmigrator isn't setting backfill flag?

This is from code review and talking with Chiyoung...

• while using memcachetest...
• add a server, rebalance, remove a server, rebalance, repeat this line.
• you'll probably see a handful of "missing data" error messages from memcachetest

Here's the theory...

When started in normal replication mode (that is, not doing a rebalance with the -t / vbucket-transfer mode flag), the vbucketmigrator isn't setting the TAP_CONNECT_FLAG_BACKFILL flag.

http://github.com/northscale/vbucketmigrator/blob/master/src/binarymessage.h#L150

That could lead to missing data (related to some other "missing data" bug after rebalancing servers out of a cluster, but I cannot find that bug at the moment).