metrics: reduce perf periodic collection interval to 3 hours from 24

metrics: reduce perf periodic collection interval to 3 hours from 24

This should increase the quantity of perf profiles collected for
chromiumos-wide-profiling by a factor of 8. Based on the current amount of
data received, this should increase the number of profiles collected to a
quantity less than it was before the collection scheduling was changed in
https://codereview.chromium.org/282093011/

TEST=Not really... This is just turning a knob. I did compile it.
BUG=chromium:413951
Committed: https://crrev.com/0f4852aec17e16678d42eb8ac8e1f7544b6740e4
Cr-Commit-Position: refs/heads/master@{#295154}

[dhsharp, 2014-09-12 23:57:09]

dhsharp@chromium.org changed reviewers:
+ isherman@chromium.org

[Ilya Sherman, 2014-09-15 23:33:23]

LGTM

[dhsharp, 2014-09-16 19:29:09]

The CQ bit was unchecked by dhsharp@chromium.org

[dhsharp, 2014-09-16 19:29:09]

The CQ bit was checked by dhsharp@chromium.org

[Ilya Sherman, 2014-09-16 20:50:00]

The CQ bit was checked by isherman@chromium.org

[commit-bot: I haz the power, 2014-09-16 20:51:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patchset/559843007/20001

[commit-bot: I haz the power, 2014-09-16 21:59:28]

Committed patchset #2 (id:20001) as 6eb3aaaffe8245e5703bdf6afff1981b64cf67d3

[commit-bot: I haz the power, 2014-09-16 22:00:39]

Patchset 2 (id:??) landed as
https://crrev.com/0f4852aec17e16678d42eb8ac8e1f7544b6740e4
Cr-Commit-Position: refs/heads/master@{#295154}