Revert of Update OTS to revision 6d2e08b

Revert of Update OTS to revision 6d2e08b (patchset #1 id:1 of https://codereview.chromium.org/1062093002/)

Reason for revert:
This CL caused many tests fail on uninit read errors reported by MSan

BUG=474597
Original issue's description:
> Update OTS to revision 6d2e08b
>
> This brings in a bugfix of checksum calculation that caused assertion
> failure on debug builds.
>
> BUG=464780
>
> Committed: https://crrev.com/3a672fe050438bc787af3f9bb652048291558c6c
> Cr-Commit-Position: refs/heads/master@{#324023}

TBR=bashi@chromium.org,ksakamoto@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=464780
Committed: https://crrev.com/2a0977c4c2dfa7614f1e0eea3d0f0c21937565b3
Cr-Commit-Position: refs/heads/master@{#324046}

[zhaoqin1, 2015-04-07 15:25:39]

Created Revert of Update OTS to revision 6d2e08b

[commit-bot: I haz the power, 2015-04-07 15:26:05]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1064913002/1

[commit-bot: I haz the power, 2015-04-07 15:27:15]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-07 15:27:59]

Patchset 1 (id:??) landed as
https://crrev.com/2a0977c4c2dfa7614f1e0eea3d0f0c21937565b3
Cr-Commit-Position: refs/heads/master@{#324046}