Revert of Stop prepending "r" to commit hashes in merge_to_branch.py

Revert of Stop prepending "r" to commit hashes in merge_to_branch.py (patchset #1 id:1 of https://codereview.chromium.org/1298973007/ )

Reason for revert:
Result when using the script:

tools/release/merge_to_branch.py
  File "tools/release/merge_to_branch.py", line 108
    self["revision_list"] = ", ".join(self["full_revision_list"]))
                                                                 ^
SyntaxError: invalid syntax

Original issue's description:
> Stop prepending "r" to commit hashes in merge_to_branch.py
>
> R=machenbach@chromium.org
>
> Committed: https://crrev.com/e5dbfd06c3dab5934e846c40af2a8b7fb5cdf0d6
> Cr-Commit-Position: refs/heads/master@{#30483}

TBR=machenbach@chromium.org,adamk@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Committed: https://crrev.com/76fb022fd257ebb9d1d31c9ec4d08332b9a86d48
Cr-Commit-Position: refs/heads/master@{#30505}

[Michael Hablich, 2015-09-01 11:10:53]

Created Revert of Stop prepending "r" to commit hashes in merge_to_branch.py

[commit-bot: I haz the power, 2015-09-01 11:10:56]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1321343002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1321343002/1

[commit-bot: I haz the power, 2015-09-01 11:11:07]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-01 11:11:22]

Patchset 1 (id:??) landed as
https://crrev.com/76fb022fd257ebb9d1d31c9ec4d08332b9a86d48
Cr-Commit-Position: refs/heads/master@{#30505}

[Michael Achenbach, 2015-09-01 11:18:15]

On 2015/09/01 11:11:22, commit-bot: I haz the power wrote:
> Patchset 1 (id:??) landed as
> https://crrev.com/76fb022fd257ebb9d1d31c9ec4d08332b9a86d48
> Cr-Commit-Position: refs/heads/master@{#30505}

lgtm - fair enough - we should have presubmit checking the syntax of all our
python scripts... so that there's no need for counting parentheses...

[Michael Hablich, 2015-09-01 11:24:48]

On 2015/09/01 11:18:15, Michael Achenbach wrote:
> On 2015/09/01 11:11:22, commit-bot: I haz the power wrote:
> > Patchset 1 (id:??) landed as
> > https://crrev.com/76fb022fd257ebb9d1d31c9ec4d08332b9a86d48
> > Cr-Commit-Position: refs/heads/master@{#30505}
> 
> lgtm - fair enough - we should have presubmit checking the syntax of all our
> python scripts... so that there's no need for counting parentheses...

Yeah uploading fix now, didn't want to leave it broken until fix lands.