MB-8161: Traverse the whole future queue when a task is woken

If a task is woken up then the future queue might not be in order
so we need to check each job in the future queue to make sure we
find all of the jobs that are ready to run.

Change-Id: I8505ba86180672dbb5092407debbbf777288155e
Reviewed-on: http://review.couchbase.org/25925
Reviewed-by: Jin Lim <jin@couchbase.com>
Tested-by: Jin Lim <jin@couchbase.com>
MB-7966 ABHINAV KVShard implementation for Multi-readers and writers

        Please read kvshard.hh for details of the new class which
        is a new abstract layer representing a logical group of
        database partitions (vbuckets)

Change-Id: I520b63a1f998020334d0d47dbb8fb3870d8312e6
MB-7966 IOManager integration with KVShard

Change-Id: I641dda9ea68bdade2f71b5805da439173dc3d678