MB-11502: Fix incorrect snap_start/end seqno's in stream retry

If we set the snap_send_seqno to always be equal to the
snap_start_seqno then it is possible that the snap_end_seqno will
be less than then start seqno and this will cause the stream
creation to fail on the producer side.

Change-Id: I73f1fdda6cf0f979c8b128f01a9366ecb6321b20
Reviewed-on: http://review.couchbase.org/38703
Reviewed-by: Sriram Ganesan <sriram@couchbase.com>
Reviewed-by: Sundararaman Sridharan <sundar@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>