Don't panic if setting vdev properties is unsupported for this vdev type

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