dm mpath: Add missing dm_put_device when failing to get scsi dh name

dm mpath: Add missing dm_put_device when failing to get scsi dh name

When commit fd81bc5cca8f ("scsi: device_handler: Return error pointer in
scsi_dh_attached_handler_name()") added code to fail parsing the path if
scsi_dh_attached_handler_name() failed with -ENOMEM, it didn't clean up
the reference to the path device that had just been taken. Fix this, and
steamline the error paths of parse_path() a little.

Fixes: fd81bc5cca8f ("scsi: device_handler: Return error pointer in scsi_dh_attached_handler_name()")
Cc: stable@vger.kernel.org
Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>