MB-8903: Return error when there's no Failover Log

If you want to receive a Failover Log (e.g. in an Stream
Request OK Response) and there is none, return an
'no_failover_log_found' error.

Change-Id: I88bb185e52c642490aed04d0e99ed9552e317814
Reviewed-on: http://review.couchbase.org/30888
Reviewed-by: Filipe David Borba Manana <fdmanana@gmail.com>
Tested-by: buildbot <build@couchbase.com>