feat(shard): queue listing from multiple sources

Sharding need special storage driver wrapper for queue-related
operations. The listing queue algorithm merges the listing result
from multiple storage connections, and return them in sorted order.

This patch also fixes non-configurable default limits in sharding.

Change-Id: If9bd80459bd1a0dc92ea68c42bc28c0f6dde2a65
Partitally-implements: blueprint storage-sharding
Merge "feat(shard): queue listing from multiple sources"