[telemetry] Don't prepend python when running gsutil on POSIX.

[telemetry] Don't prepend python when running gsutil on POSIX.

We have a bot that's using a shell script as a symlink. So Telemetry should just run it as an executable, not as a Python script.

BUG=None.
TEST=None.

Committed: https://crrev.com/3070a949bf88672ffabd6b1e1f93bd59b07df5be
Cr-Commit-Position: refs/heads/master@{#332251}

[eakuefner, 2015-06-01 18:28:46]

eakuefner@chromium.org changed reviewers:
+ eakuefner@chromium.org

[eakuefner, 2015-06-01 18:28:46]

lgtm watttt

[dtu, 2015-06-01 18:30:16]

The CQ bit was checked by dtu@chromium.org

[commit-bot: I haz the power, 2015-06-01 18:33:03]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1150723006/1

[commit-bot: I haz the power, 2015-06-01 19:59:20]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-01 20:00:36]

Patchset 1 (id:??) landed as
https://crrev.com/3070a949bf88672ffabd6b1e1f93bd59b07df5be
Cr-Commit-Position: refs/heads/master@{#332251}