pnfs/blocklayout: Fix memory leak in bl_parse_scsi()

pnfs/blocklayout: Fix memory leak in bl_parse_scsi()

In bl_parse_scsi(), if the block device length is zero, the function
returns immediately without releasing the file reference obtained via
bl_open_path(), leading to a memory leak.

Fix this by jumping to the out_blkdev_put label to ensure the file
reference is properly released.

Fixes: d76c769c8db4c ("pnfs/blocklayout: Don't add zero-length pnfs_block_dev")
Signed-off-by: Zilin Guan <zilin@seu.edu.cn>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>