crosperf: Disable ASLR in crosperf by default

Disabling Address Space Layout Randomization (ASLR) can reduce
much variance when measuring performance of benchmark from run
to run. This CL will disable ASLR in crosperf by default and
add a flag '--enable_aslr' for users to enable it for other
testing purpose.

BUG=chromium:930332
TEST=Tested locally for several boards and several benchmarks

Change-Id: Icfbe477a99ef9a68b503e4979cf2ff47d07a128f
Reviewed-on: https://chromium-review.googlesource.com/1398522
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Tiancong Wang <tcwang@google.com>
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
6 files changed