[Telemetry] Refactor common Android test harness functions.

[Telemetry] Refactor common Android test harness functions.

This is a reland of crrev.com/62953024 which was reverted because
it broke other platforms.

Refactoring common cleanup code required by both
android_browser_finder.py and perf/setup.py and moving it into
pyblib/utils/test_environment.py.
Also, this change avoids killing twice the adb server when running
in a bot environment, where the adb restart is already invoked by
the bot steps.

BUG=268450
R=bulach@chromium.org,tonyg@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=237815

[Primiano Tucci (use gerrit), 2013-11-28 13:19:40]

The previous CL (crrev.com/62953024) was reverted because it was sadly breaking
ChromiumOS [1] and XP bots [2] due to the imports in android_browser_finder. 

Using now adb_commands, as suggested, to proxy calls to
CleanupLeftoverProcessesl.

Patch-set 2 is the delta vs the previous CL.

[1]
http://build.chromium.org/p/chromium.chromiumos/builders/ChromiumOS%20%28amd6...
[2]
http://build.chromium.org/p/chromium.perf/builders/XP%20Perf%20%285%29/builds...

[bulach, 2013-11-28 14:36:56]

lgtm % nits, thanks!

https://codereview.chromium.org/94683002/diff/30006/tools/telemetry/telemetry...
File tools/telemetry/telemetry/core/backends/adb_commands.py (left):

https://codereview.chromium.org/94683002/diff/30006/tools/telemetry/telemetry...
tools/telemetry/telemetry/core/backends/adb_commands.py:33: 
nit: keep it :)
also need to add an extra \n before and after CleanupLeftoverProcesses, i.e.,
style says two \n around top-levels.

[Primiano Tucci (use gerrit), 2013-11-28 15:10:56]

On 2013/11/28 14:36:56, bulach wrote:
> lgtm % nits, thanks!
> 
>
https://codereview.chromium.org/94683002/diff/30006/tools/telemetry/telemetry...
> File tools/telemetry/telemetry/core/backends/adb_commands.py (left):
> 
>
https://codereview.chromium.org/94683002/diff/30006/tools/telemetry/telemetry...
> tools/telemetry/telemetry/core/backends/adb_commands.py:33: 
> nit: keep it :)
> also need to add an extra \n before and after CleanupLeftoverProcesses, i.e.,
> style says two \n around top-levels.

Oops sorry, I didn't realize the global methods were considered top levels. My
bad, I should have realized looking at the ones below! Thanks.

[commit-bot: I haz the power, 2013-11-28 15:12:09]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/primiano@chromium.org/94683002/90001

[commit-bot: I haz the power, 2013-11-28 18:02:34]

Change committed as 237815