For the TestDeviceStressTest is the new CTS test case in Android 4.3,

this test  want test the stability of the adb push/rm , it make 200
little files and try to push it to /storage/sdcard0 and then rm it, this
step need repeat 50 times in 10 mins.
But for some OEM, the sdcard performance may be poor, some device
need 15mins to finish this test without any adb issue. But because the
time is too long,which cause the test can not finished in 10 mins
, therefore this test case always result failed in most of our
devices.
So in order to compatible most of the Android device, I submit
the patch to reduce the test times from 50 to 25 times. I do think
it will benifit
more manufactory and meanwhile with no side-effect for
the really test result.

Change-Id: I75b3eb0be78298c993bd58e5ca4c6726023cddba