Rename virtutils to the more common libvirt_utils

`libvirt_utils` is the more prevalent alias in the code for the module, so
rename `virtutils` to match.

Change-Id: Ib8d4291866bc53fa1980b70dd0f12e6b1fe10436
Add i18n log markers in disk api

    Improve LOG i18n log markers in nova/virt/disk/api.py.

Change-Id: I76b5a2acc15bd4230ea6e243770ac0590c56235d
Merge "Add i18n log markers in disk api"
Merge "Rename virtutils to the more common libvirt_utils"