Adds 'sata' as a valid disk bus for qemu and kvm hypervisors

Reasoning:
- Setting custom properties on glance images allows us to select the
type of disk bus e.g. VIRTIO/IDE/SCSI.
Although SATA disk bus works perfectly for qemu/kvm, it is not allowed
due to a check in virt/libvirt/blockinfo.py : is_disk_bus_valid_for_virt
- some Linux (custom) images require use of SATA bus rather than any
other that seems to be allowed.

Change-Id: Ie32ff7acf31d80d4fc1adbeadaaf30a886d10e49
Closes-Bug: #1686136

nova/tests/unit/virt/libvirt/test_blockinfo.py

@@ -844,7 +844,9 @@ class LibvirtBlockInfoTest(test.NoDBTestCase):
                  'disk_bus': 'scsi',
                  'boot_index': 1,
                  'device_type': 'lame_type',
-                 'delete_on_termination': True}]
+                 'delete_on_termination': True},
+                {'disk_bus': 'sata', 'guest_format': None,
+                 'device_name': '/dev/sda', 'size': 3}]
         expected = [{'dev': 'vds', 'type': 'disk', 'bus': 'usb'},
                     {'dev': 'vdb', 'type': 'disk',
                      'bus': 'virtio', 'format': 'ext4'},
@@ -852,7 +854,8 @@ class LibvirtBlockInfoTest(test.NoDBTestCase):
                     {'dev': 'sdr', 'type': 'cdrom',
                      'bus': 'scsi', 'boot_index': '1'},
                     {'dev': 'vdo', 'type': 'disk',
-                     'bus': 'scsi', 'boot_index': '2'}]
+                     'bus': 'scsi', 'boot_index': '2'},
+                    {'dev': 'sda', 'type': 'disk', 'bus': 'sata'}]
 
         image_meta = objects.ImageMeta.from_dict(self.test_image_meta)
         for bdm, expected in zip(bdms, expected):

nova/virt/libvirt/blockinfo.py

@@ -197,8 +197,8 @@ def find_disk_dev_for_disk_bus(mapping, bus,
 
 def is_disk_bus_valid_for_virt(virt_type, disk_bus):
     valid_bus = {
-        'qemu': ['virtio', 'scsi', 'ide', 'usb', 'fdc'],
-        'kvm': ['virtio', 'scsi', 'ide', 'usb', 'fdc'],
+        'qemu': ['virtio', 'scsi', 'ide', 'usb', 'fdc', 'sata'],
+        'kvm': ['virtio', 'scsi', 'ide', 'usb', 'fdc', 'sata'],
         'xen': ['xen', 'ide'],
         'uml': ['uml'],
         'lxc': ['lxc'],

releasenotes/notes/bug-1686136-b07bef4c56e92b31.yaml

@@ -0,0 +1,7 @@
+---
+other:
+  - Adds 'sata' as a valid disk bus for qemu and kvm hypervisors.
+    Setting the 'hw_disk_bus' custom property on glance images allows for
+    selecting the type of disk bus e.g. VIRTIO/IDE/SCSI. Some Linux (custom)
+    images require use of SATA bus rather than any other that seem to be
+    allowed.