Fix flag copying in resume case

A couple flags weren't being copied in the case where we're doing size
estimation on a resume.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Signed-off-by: Paul Dagnelie <pcd@delphix.com>
Closes: #12266