MB-11410: Use last persisted seqno as end seqno for disk only upr stream

This will allow upr streams to function properly when a consumer
requests a disk only snapshot and the flusher is paused. Note that
this is also more correct in terms of what the disk only stream is
going to send anyways.

Change-Id: If532a0d0b93a23adf76e7754eae127c0ae917a87
Reviewed-on: http://review.couchbase.org/39166
Reviewed-by: David Liao <david.liao@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>