Add an option for virsh undefine command, to remove associated storage
volumes while undefining a domain. This patch allows the user to remove
associated (libvirt managed ) storage volumes while undefining a domain.

The new option --storage for the undefine command takes a string
argument that consists of comma separated list of target or source path
of volumes to be undefined. Volumes are removed after the domain has
been successfully undefined,

If a volume is not part of a storage pool, the user is warned to remove
the volume in question himself.

Option --wipe-storage may be specified along with this, that ensures
the image is wiped before removing.

Option --remove-all-storage enables the user to remove all storage. The
name is chosen long as the users should be aware what they're about to
do.