dm: fix bug with RCU locking in dm_blk_report_zones

The dm_get_live_table() function makes RCU read lock so
dm_put_live_table() must be called even if dm_table map is not found.

Fixes: e76239a3 ("block: add a report_zones method")
Cc: stable@vger.kernel.org
Signed-off-by: Sergei Shtepa <sergei.shtepa@veeam.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>