Adds Ironic test_baremetal_basic_ops scenario test

Adds an Ironic scenario test that validates a full instance
boot using Ironic.  In addition to verifying the Nova instance
boots and has connectivity, it monitors power and state transitions
on the Ironic side.  It currently validates orchestration of the pxe_ssh
driver but the goal would be to support other drivers, and test them
conditionally based on the driver associated with the configured Ironic
node.

Change-Id: I7a98ab9c771fe17387dfb591df5a40d27194a5c8
Volume size could be specified to create volume

1. Provide a "volume_size" config at VolumeGroup
2. Make size as optional prameter, modify all volumes_client to
read the size from CONf if size is None.
3. Modify the testcase: test_volume_create_get_update
_delete_from_image to call create_volume with no size
parameter specified.

Change-Id: I2897f6d6bd970f73867f56d9d23a768cafcbfd80
Closes-Bug: #1293885
Merge "Adds Ironic test_baremetal_basic_ops scenario test"
Merge "Volume size could be specified to create volume"