Exclude non-bootable storage template from image-topology
Exclude non-bootable storage template from image-topology

PowerVC 1.2.3 added complex boot/data volume concepts and it's image
accessible storage connective group's volume type API will return all
volume types for boot and data volume, we expose the PowerVC storage
templates in image's image-topology property and that property need only
include the bootable storage templates based on PowerVC 1.2.3 introduced
boot/data volume concept as we just expose the volume only for boot
volume at this time. The fix is just to exclude the SCG accessible
storage template via it's
['extra_specs']['capabilities:volume_backend_name'] property, and only
include the the storage template with such property value in SCG's
boot_providers list which means that volume type is a bootable volume
types. If SCG does not have such boot_providers property, then we just
ignore such checking.

Close-Bug: #1460563
Change-Id: Ifa608a514ec70b831d04802b728dff14864578ab

openstack/powervc-driver,openstack/powervc-driver,stackforge/powervc-driver,stackforge/powervc-driver