use sh instead of bash in ProcessUtilTest on linux

use sh instead of bash in ProcessUtilTest on linux

These unit tests don't seem to really depend on bash, by using sh
instead of bash we can run these on more embedded linux targets.

Committed: https://crrev.com/69ce035ff23d7712724772dc8eb0379951abb904
Cr-Commit-Position: refs/heads/master@{#339901}

[Mostyn Bramley-Moore, 2015-07-22 11:45:57]

mostynb@opera.com changed reviewers:
+ brettw@chromium.org, jingzhao@chromium.org

[Mostyn Bramley-Moore, 2015-07-22 11:45:57]

@brettw: please take a look.  It seems that we use sh on android, so it's
unlikely that we really need bash on linux.

[brettw, 2015-07-22 16:03:32]

lgtm

[Mostyn Bramley-Moore, 2015-07-22 16:56:53]

The CQ bit was checked by mostynb@opera.com

[commit-bot: I haz the power, 2015-07-22 16:57:28]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1249973002/1

[commit-bot: I haz the power, 2015-07-22 17:28:17]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-07-22 17:28:59]

Patchset 1 (id:??) landed as
https://crrev.com/69ce035ff23d7712724772dc8eb0379951abb904
Cr-Commit-Position: refs/heads/master@{#339901}