MB-9118 Add API to rewind handle to next-oldest header

Change-Id: I81c46dd0f6d928b163fb3b379e4ad4562b3144dd
Reviewed-on: http://review.couchbase.org/32364
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Volker Mische <volker.mische@gmail.com>