MB-8903: Supply full failover log to enum_docs_since/7

Instead of supplying just the most recent partition version,
supply the full failover log. This way the `enum_docs_since`
can retry with different partition versions.

Change-Id: I2d85def31a094998268f4cceec7dc03944c22ef0
Reviewed-on: http://review.couchbase.org/31299
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Filipe David Borba Manana <fdmanana@gmail.com>