[SCSI] libosd: Add Flush and List-objects support

Add support for the various List-objects commands. List-partitions-in-device,
List-collections-in-partition, List-objects-in-partition,
List-objects-in-collection. All these support partial listing and continuation.

Add support for the different Flush commands and options.

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
Reviewed-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>