LU-734 tests: save recovery-*-scale debug logs into $LOGDIR

LU-734 tests: save recovery-*-scale debug logs into $LOGDIR

This patch changes the specific debug log names of
recovery-*-scale tests and saves them into $LOGDIR.

Signed-off-by: Yu Jian <yujian@whamcloud.com>
Change-Id: Id1ad7dd3dde41bd49a53986945d15d80f91718e5
Reviewed-on: http://review.whamcloud.com/2261
Reviewed-by: Minh Diep <mdiep@whamcloud.com>
Reviewed-by: Cliff White <cliffw@whamcloud.com>
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>