btrfs/237: skip test on devices with conventional zones

btrfs/237: skip test on devices with conventional zones

Skip btrfs/237 on devices with conventional zones, as we cannot force data
allocation on a sequential zone at the moment and conventional zones
cannot be reset, making the test invalid.

Furthermore limit the output of get_data_bg() and get_data_bg_physical()
to the first address.

Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>