If we're creating a pool with version >= SPA_VERSION_DSL_SCRUB (v11)
we need to account for additional space needed by the origin dataset
which will also be snapshotted: "poolname"+"/"+"$ORIGIN"+"@"+"$ORIGIN".
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Signed-off-by: loli10K <ezomori.nozomu@gmail.com>
Closes#6374