MB-10904: allow reading nonactive data out of couchstore files

Change-Id: I9741ae4c469d86164b136a58f613f10ce81426c0
Reviewed-on: http://review.couchbase.org/36123
Reviewed-by: Bin Cui <bin.cui@gmail.com>
Tested-by: Bin Cui <bin.cui@gmail.com>