LU-980 llog: cleanup return value in llog_client_create

in llog_client_create, the newly allocated llog_handle is
return by parameter res, but it doesn't be cleaned up
if the following operations failed and the corresponding
llog_handle is already freed.

Signed-off-by: Hongchao Zhang <hongchao.zhang@whamcloud.com>
Change-Id: I8b59dfde91da2c20881f29e8ff46a0a93f0ee1b2
Reviewed-on: http://review.whamcloud.com/1958
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Fan Yong <yong.fan@whamcloud.com>
Reviewed-by: Bobi Jam <bobijam@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>