LU-357 racer test cleanup

LU-357 racer test cleanup
 1, increase the test time to 300s(900s for SLOW)
 2, fixing the problem of recursively calling racer.sh

Change-Id: I91ac7e5c42ed5bc98b3a647c30d7e37af0573f09
Signed-off-by: Hongchao Zhang <hongchao.zhang@whamcloud.com>
Reviewed-on: http://review.whamcloud.com/905
Reviewed-by: Yu Jian <yujian@whamcloud.com>
Reviewed-by: Fan Yong <yong.fan@whamcloud.com>
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>