LU-1018 tests: reduce runtime value for compilebench

LU-1018 tests: reduce runtime value for compilebench

We are reducing the cbench_IDIRS and cbench_RUNS to 2.
These variables can be adjusted to other runs beside
sanity check.

Test-Parameters: envdefinitions=SLOW=yes,ENABLE_QUOTA=yes testlist=parallel-scale
Signed-off-by: Minh Diep <minh.diep@intel.com>
Change-Id: I6613c9d0245d6c49c8d94f1252eb13ac87a621a1
Reviewed-on: http://review.whamcloud.com/5032
Tested-by: Hudson
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Emoly Liu <emoly.liu@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Johann Lombardi <johann.lombardi@intel.com>