LU-1018 test: Reduce compilebench run time

LU-1018 test: Reduce compilebench run time

We decided to reduce the run time for compilebench
so it would run under 1h on VM nodes. This is similar
to master

Signed-off-by: Minh Diep <mdiep@whamcloud.com>
Change-Id: Ie664ad131e4fbce9443eb78d06cbe36d6002b881
Reviewed-on: http://review.whamcloud.com/2005
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Cliff White <cliffw@whamcloud.com>
Reviewed-by: Wei Liu <sarah@whamcloud.com>
Reviewed-by: Johann Lombardi <johann@whamcloud.com>