GPFS support for various volume attributes

GPFS support for various volume attributes

Specify the following attributes when creating a new volume:

* The storage pool on which the volume is placed
* Number of block-level replicas
* Whether the physical blocks should be allocated locally on the node issuing
  the IO or striped across the cluster
* Whether writes to the volume should use direct IO
* Number of file system blocks to be laid out sequentially on disk to behave
  like a single large block
* Local storage attached to specific node(s) where the replicas of the
  volume should be allocated

Change-Id: I77bb7de32bbde5a125f8c6f9a727b538ea99bc18
Implements: blueprint gpfs-volume-attributes