Add 'COMPUTE_STORAGE_VIRTIO_FS', 'COMPUTE_MEM_BACKING_FILE'

COMPUTE_STORAGE_VIRTIO_FS allows us to report this trait and use
it to filter hosts that support virtio filesystems.

COMPUTE_MEM_BACKING_FILE allows us to report this trait and use
it to filter hosts that supports file-backed memory.

These both traits are necessary to support sharing files with
virtiofs and so forth with manila shares.

Implements: blueprint libvirt-virtiofs-attach-manila-shares
Change-Id: I89419cf1649f48106d84cc84e688df7a065f470a

os_traits/compute/__init__.py

@@ -37,5 +37,8 @@ TRAITS = [
     'SOCKET_PCI_NUMA_AFFINITY',
     # The compute manager supports handling remote_managed PCI devices
     # associated with SmartNIC DPUs.
-    'REMOTE_MANAGED_PORTS'
+    'REMOTE_MANAGED_PORTS',
+    # The compute manager is configured to support file-backed memory.
+    # https://docs.openstack.org/nova/latest/admin/file-backed-memory.html
+    'MEM_BACKING_FILE',
 ]

os_traits/compute/storage.py

@@ -25,4 +25,6 @@ TRAITS = [
     'BUS_VIRTIO',
     'BUS_UML',
     'BUS_XEN',
+    # The compute manager supports virtio filesystems.
+    'VIRTIO_FS',
 ]