Libvirt: SMB volume driver

Currently, there are Libvirt volume drivers that support
network-attached file systems such as Gluster or NFS. This patch
adds a new volume driver in order to support attaching volumes
hosted on SMB shares.

Co-Authored-By: Gabriel Samfira <gsamfira@cloudbasesolutions.com>

DocImpact

Change-Id: I1db3d2a6d8ee94932348c63cc03698fdefff0b5c
Implements: blueprint libvirt-smbfs-volume-support
Merge "Libvirt: SMB volume driver"