imsm: add --update=uuid support

imsm: add --update=uuid support

When disks have conflicting container memberships (same container ids
but incompatible member arrays) --update=uuid can be used to move
offenders to a new container id by changing 'orig_family_num'.

Note that this only supports random updates of the uuid as the actual
uuid is synthesized.  We also need to communicate the new
'orig_family_num' value to all disks involved in the update.  A new
field 'update_private' is added to struct mdinfo to allow this
information to be transmitted.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>