- skip length_idx index for a replaced variable-sized attribute
- skip length_idx index for a removed variable-sized attribute
- also re-arranged code to make sure that length_idx is always
incremented for variable-sized attributes
- additionally add an assertion that the number of actually produced
attributes is the same as the expected number of resulting
attributes
In cooperation with: Matthew Ahrens <mahrens@delphix.com>
Tested by: Trent Nelson <trent@snakebite.org>
Reviewed by: Matthew Ahrens <mahrens@delphix.com> (for upstream)
To do: get this upstreamed
MFC after: 2 weeks
a7cf665d5f