CQ: Remove baremetal machines from CQ bots.

CQ: Remove baremetal machines from CQ bots.

The baremetal machines rarely catch any issues that are caught
by the other bots and are currently the bottleneck of the CQ.
Since they still run in client.webrtc and there also produces
perf data, I think it makes sense to exclude them from the CQ.

It is still possible to run tryjobs on them using:
git try --bot=linux_baremetal --bot=win_baremetal --bot=mac_baremetal

R=phoglund@webrtc.org

Committed: https://crrev.com/d2320cee876b6af48207d021f78aa8759976319c
Cr-Commit-Position: refs/heads/master@{#9970}

[kjellander_webrtc, 2015-09-17 11:55:47]

kjellander@webrtc.org changed reviewers:
+ phoglund@webrtc.org

[phoglund, 2015-09-17 12:33:19]

lgtm

[commit-bot: I haz the power, 2015-09-17 12:34:30]

Patchset 1 (id:??) landed as
https://crrev.com/d2320cee876b6af48207d021f78aa8759976319c
Cr-Commit-Position: refs/heads/master@{#9970}

[kjellander_webrtc, 2015-09-17 12:34:32]

Committed patchset #1 (id:1) manually as
d2320cee876b6af48207d021f78aa8759976319c (presubmit successful).