Check that vdev has valid zap and bail out early.
While here, move objid selection out of the loop, it's not going to
change.
Reviewed-by: Allan Jude <allan@klarasystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Yuri Pankov <yuripv@FreeBSD.org>
Closes#15063
1a2e486d25