crosperf: Ignore error when disabling turbo.

Some boards do not permit changing tubo config
/sys/devices/system/cpu/intel_pstate/no_turbo
Ignore the error for now so that tests can continue.

Also update some formatting suggested by tc_format.

BUG=chromium:839125
TEST=No more errors.

Change-Id: I3a709ea2638d783dd3a3ebf70eba8a6dbc4df53a
Reviewed-on: https://chromium-review.googlesource.com/1040773


Commit-Queue: Manoj Gupta <manojgupta@chromium.org>
Tested-by: Manoj Gupta <manojgupta@chromium.org>
Trybot-Ready: Manoj Gupta <manojgupta@chromium.org>
Reviewed-by: Luis Lozano <llozano@chromium.org>