Revert of use (num_cores/2) jobs by default for telemetry unittests.

Revert of use (num_cores/2) jobs by default for telemetry unittests. (patchset #1 id:1 of https://codereview.chromium.org/742373002/)

Reason for revert:
May be causing failures on XP Tests bot:
https://build.chromium.org/p/chromium.win/builders/XP%20Tests%20(1)

First failure here:
https://build.chromium.org/p/chromium.win/builders/XP%20Tests%20%281%29/builds/34002

Speculative revert after discussions.

Original issue's description:
> use (num_cores/2) jobs by default for telemetry unittests.
>
> Previously we were using (num_cores/4). Let's see if we can get more
> parallelism and still not overload the machine.
>
> R=dtu@chromium.org
> BUG=388256
>
> Committed: https://crrev.com/4866abd7d1c6bfeb520ccd74ffb730ed45dd3cf3
> Cr-Commit-Position: refs/heads/master@{#305163}

TBR=dtu@chromium.org,tonyg@chromium.org,dpranke@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=388256
Committed: https://crrev.com/d5ab562fd38ae1591536c7f85fa8c81a05145370
Cr-Commit-Position: refs/heads/master@{#305231}

[Roger Tawa OOO till Jul 10th, 2014-11-21 17:28:48]

Created Revert of use (num_cores/2) jobs by default for telemetry unittests.

[commit-bot: I haz the power, 2014-11-21 17:29:54]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/748073003/1

[commit-bot: I haz the power, 2014-11-21 17:30:34]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-11-21 17:31:17]

Patchset 1 (id:??) landed as
https://crrev.com/d5ab562fd38ae1591536c7f85fa8c81a05145370
Cr-Commit-Position: refs/heads/master@{#305231}